I'm currently creating a custom report for a module. I use Odoo 8.

This is my code :

sale_plan_emballage_report.xml :

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <report 
            id="plan_emballage_qweb_id"
            model="sale.order.line"
            string="Sale plan emballage with QWeb"
            report_type="qweb-pdf"
            file="sale_plan_emballage.mysaleplanemballage_report"
            name="sale_plan_emballage.plan_emballage_qweb"
        />

        <template id="plan_emballage_qweb">
            <t t-call="report.external_layout">
                <div class="page">
                    <h3 align="center"> Production d'emballage par commande – Semaine <span t-esc="hello_world()"/> </h3>
                    <h4 align="center"> <strong>Requis Pour Lundi [[get_FirstDateOfWeek(0, False)]]</strong> </h4>

                    <table class="table" border="1">
                        <thead>
                            <tr>
                                <th>Item</th>
                                <th class="text-center">Qté</th>
                                <th class="text-center">Metal</th>
                                <th class="text-center">Bois</th>
                                <th class="text-center">Tissus</th>
                                <th class="text-center">PG</th>
                                <th class="text-center">Pattes</th>
                                <th class="text-center">Config</th>
                            </tr>
                        </thead>
                        <tbody>
                            <tr>
                                <td>Item</td>
                                <td class="text-center">Qté</td>
                                <td class="text-center">Metal</td>
                                <td class="text-center">Bois</td>
                                <td class="text-center">Tissus</td>
                                <td class="text-center">PG</td>
                                <td class="text-center">Pattes</td>
                                <td class="text-center">Config</td>
                            </tr>
                        </tbody>
                    </table>


                </div>
            </t>
        </template>

plan.py :

# -*- coding: utf-8 -*-
from openerp.report import report_sxw
from openerp import models #MK
from openerp.osv import osv #MK
import time
import datetime

class plan(report_sxw.rml_parse):
    def __init__(self, cr, uid, name, context=None):
        super(plan, self).__init__(cr, uid, name, context=context)
        self.localcontext.update({
            'time': time,
            'get_jours':self._get_jours,
            'get_OrdersJour':self._get_OrdersJour,
            'get_LinesOrderJour':self._get_LinesOrderJour,
            'get_FirstDateOfWeek':self._get_FirstDateOfWeek,
            'getLines': self.getLines,
            'getLinesBois': self.getLinesBois,
            'getLinesMetal': self.getLinesMetal,
            'getLinesTissus': self.getLinesTissus,
            'getLinesTeint': self.getLinesTeint,
            'getLinesPeint': self.getLinesPeint,
            'hello_world': self._hello_world, #MK
        })

    tabMoisFr = ['janvier','fevrier','mars','avril','mai','juin','juillet','aout','septembre','octobre','novembre','decembre']

    def _get_FirstDateOfWeek(self, offset=0, year=True):
        today = datetime.date.today()
        first = today - datetime.timedelta(days=today.weekday()-offset)

        ret = str(first.day) + ' ' + self.tabMoisFr[first.month-1]

        if year:
            ret += ' ' + str(first.year)

        return ret


    tabJour = ['Lundi','Mardi','Mercredi','Jeudi','Vendredi','Samedi','Dimanche']


    def getLinesTissus (self, objects):
        obj = self.getFctFiltre('tissu')(objects)

        return self.checkQtyField(self.getLines(obj),'qtyRembourage')

    def getLinesMetal (self, objects):
        obj = self.getFctFiltre('metal')(objects)


        return self.checkQtyField(self.getLines(obj),'qtyMetal')

    def getLinesBois (self, objects):
        obj = self.getFctFiltre('bois')(objects)

        return self.checkQtyField(self.getLines(obj),'qtyBois')

    def getLinesTeint (self, objects):
        obj = self.getFctFiltre('bois')(objects)

        return self.checkQtyField(self.getLines(obj),'qtyTeinture')

    def getLinesPeint (self, objects):
        obj = self.getFctFiltre('metal')(objects)

        return self.checkQtyField(self.getLines(obj),'qtyPeinture')

    def checkQtyField (self, objects, field):

        for i in range(len(objects)):

            for cmd in objects[i]['commandes'].keys():
                removeItem = 0

                for j in range(len (objects[i]['commandes'][cmd]['items'])):
                    if objects[i]['commandes'][cmd]['items'][j - removeItem][field] <= 0:
                        del objects[i]['commandes'][cmd]['items'][j - removeItem]
                        removeItem += 1

                if len (objects[i]['commandes'][cmd]['items']) == 0:
                    del objects[i]['commandes'][cmd]



        return objects

    def getLines (self, objects):

        tabData = []
        print objects
        for i in range (7):
            tabData.append({})
            tabData [i] ['jour']      = self.tabJour [i]
            tabData [i] ['commandes'] = {}

        for o in objects:
            indJour = int(o.jour) - 1

            if indJour not in range(7): continue

            commande = o.order_id.name
            print "yyyyyyyyyyyyoooooooooooooooooooooolllllllllllllllllllllooooooooooooooooooooooooooo"
            if not (tabData [indJour]['commandes'].has_key (commande)):
                tabData [indJour]['commandes'][commande] = {}
                tabData [indJour]['commandes'][commande]['items'] = []
                tabData [indJour]['commandes'][commande]['partner'] = o.order_partner_id.name




            bois    = o.bois1.code_fini
            bois2   = o.bois2.code_fini
            metal   = o.metal.code_fini
            tissus  = o.tissu.code_fini
            poignee = o.poignee.code_fini
            patte   = o.patte.code_fini
            cfg     = o.config


            optionTissu = o.tissu.couleur_finifr

            qty           = int(o.product_uom_qty)
            qtyEmballe    = o.qte_emb and int(o.qte_emb) or 0
            qtyPeinture   = qty - qtyEmballe - int(o.FabPeint)
            qtyTeinture   = qty - qtyEmballe - int(o.FabTeint)
            qtyRembourage = qty - qtyEmballe - int(o.ProdFTissus)
            qtyMetal      = qtyPeinture - int(o.ProdFMetal)
            qtyBois       = qtyTeinture - int(o.ProdFBois)

            if not (qtyMetal) or qtyMetal < 0:
                qtyMetal = 0
            if not (qtyBois) or qtyBois < 0:
                qtyBois = 0
            if not (qtyPeinture) or qtyPeinture < 0:
                qtyPeinture = 0
            if not (qtyTeinture) or qtyTeinture < 0:
                qtyTeinture = 0
            if not (qtyRembourage) or qtyRembourage < 0:
                qtyRembourage = 0

            if bois == '.':
                bois = None
            if bois2 == '.':
                bois2 = None
            if metal == '.':
                metal = None
            if tissus == '.':
                tissus = None
            if poignee == '.':
                poignee = None
            if patte == '.':
                patte = None
            if cfg == '.':
                cfg = None

            if optionTissu == "NONE":
                optionTissu=None

            tabData [indJour]['commandes'][commande]['items'].append ({
                    'item': o.product_id.default_code,
                    'qty': qty,
                    'metal': metal,
                    'bois': bois,
                    'bois2': bois2,
                    'tissus': tissus,
                    'poignee': poignee,
                    'patte': patte,
                    'optionTissu': optionTissu,
                    'cfg': cfg,
                    'notes': o.notes,
                    'qtyEmballe': qtyEmballe,
                    'qtyMetal': qtyMetal,
                    'qtyBois': qtyBois,
                    'qtyPeinture': qtyPeinture,
                    'qtyTeinture': qtyTeinture,
                    'qtyRembourage': qtyRembourage,
                })
        print "FIN"
        return tabData

    def getStrJour (self, i):

        jour = False

        if 0 <= i and i <= 7:
            jour = self.tabJour[int(i) - 1]
        return jour

    def getIndJour (self, jour):        
        try:
            return self.tabJour.index(jour) + 1
        except:
            return False

    def noFilter(self, objects):
        return objects    

    def filtreBois (self, objects):
        return filter(lambda l: l.bois1.code_fini != None and l.bois1.code_fini != '.', objects)

    def filtreMetal (self, objects):
        return filter(lambda l: l.metal.code_fini != None and l.metal.code_fini != '.', objects)

    def filtreTissus (self, objects):
        return filter(lambda l: l.tissu.code_fini != None and l.tissu.code_fini != '.', objects)

    def getFctFiltre(self, filtre):
        ret = self.noFilter
        if filtre == 'bois':
            ret = self.filtreBois
        elif filtre == 'metal':
            ret = self.filtreMetal
        elif filtre == 'tissu':
            ret = self.filtreTissus
        elif filtre == 'all':
            ret = self.noFilter        
        return ret;

    def _get_jours(self, objects, filtre):

        obj = self.getFctFiltre(filtre)(objects)

        if obj == None: return False
        res=[]
        try: 
            tabOrder = []
            for o in obj:
                if o.jour is not False and o.jour not in tabOrder:
                    tabOrder.append(o.jour)
            tabOrder.sort()

            for i in tabOrder:
                res.append( (i, self.getStrJour(int(i)) ) )

        except:
            return False

        return res

    def _get_OrdersJour (self, objects, jour, filtre):

        ids = []
        ret = []
        obj = self.getFctFiltre(filtre)(objects)

        for o in obj:
            if o.jour != jour: continue
            if o.order_id.id not in ids:
                ids.append (o.order_id.id)
                ret.append ((o.order_id.id, o.order_id.name))

        return ret

    def getInfosBois(self, o):

        bois1   = o.bois1.code_fini
        bois2   = o.bois2.code_fini
        poignee = o.poignee.code_fini
        patte   = o.patte.code_fini
        cfg     = o.config

        if bois1 == '.':
            bois1 = None
        if bois2 == '.':
            bois2 = None
        if poignee == '.':
            poignee = None
        if patte == '.':
            patte = None
        if cfg == '.':
            cfg = None

        return (o.product_id.default_code, o.product_uom_qty, bois1, bois2, poignee, patte, cfg, o.order_partner_id.name, o.notes)

    def getInfosMetal(self, o):

        metal   = o.metal.code_fini
        poignee = o.poignee.code_fini
        patte   = o.patte.code_fini
        cfg     = o.config
        qty     = o.product_uom_qty - o.FabPeint - o.ProdFMetal

        if metal == '.':
            metal = None
        if poignee == '.':
            poignee = None
        if patte == '.':
            patte = None
        if cfg == '.':
            cfg = None

        return (o.product_id.default_code, qty, metal, poignee, patte, cfg, o.order_partner_id.name, o.notes)

    def getInfosTissu(self, o):

        tissu   = o.tissu.code_finifr
        nomTissu = o.tissu.couleur_finifr

        if tissu == '.':
            tissu = None

        return (o.product_id.default_code, o.product_uom_qty, tissu,nomTissu, o.order_partner_id.name, o.notes)

    def getInfos(self, o):

        bois    = o.bois1.code_fini
        metal   = o.metal.code_fini
        tissus  = o.tissu.code_fini
        poignee = o.poignee.code_fini
        patte   = o.patte.code_fini
        cfg     = o.config

        if bois == '.':
            bois = None
        if metal == '.':
            metal = None
        if tissus == '.':
            tissus = None
        if poignee == '.':
            poignee = None
        if patte == '.':
            patte = None
        if cfg == '.':
            cfg = None

        return (o.product_id.default_code, o.product_uom_qty, '', metal, bois, tissus, poignee, patte, cfg, o.order_partner_id.name, o.notes)

    def getInfosFiltre(self, filtre):
        ret = self.getInfos
        if filtre == 'bois':
            ret = self.getInfosBois
        elif filtre == 'metal':
            ret = self.getInfosMetal
        elif filtre == 'tissu':
            ret = self.getInfosTissu
        elif filtre == 'all':
            ret = self.getInfos

        return ret;

    def _get_LinesOrderJour(self, objects, order, jour, filtre):

        ret = []
        obj = self.getFctFiltre(filtre)(objects)

        for o in obj:
            if o.jour != jour or o.order_id.id != order: continue

            ret.append(self.getInfosFiltre(filtre)(o))

        return ret
    def _hello_world(self):
            return "Hello World!"
#MK
class report_saleorderqweb(models.AbstractModel):
    _name = 'report.sale_plan_emballage.plan_emballage_qweb'
    _inherit = 'report.abstract_report'
    _template = 'sale_plan_emballage.plan_emballage_qweb'
    _wrapped_report_class = plan

report_sxw.report_sxw('report.plan_teinture', 'sale.order.line', 'addons/sale_plan_emballage/report/plan_teinture.rml', parser=plan, header="external")
report_sxw.report_sxw('report.plan_peinture', 'sale.order.line', 'addons/sale_plan_emballage/report/plan_peinture.rml', parser=plan, header="external")
report_sxw.report_sxw('report.plan_rembourage', 'sale.order.line', 'addons/sale_plan_emballage/report/plan_rembourage.rml', parser=plan, header="external")
report_sxw.report_sxw('report.plan_metal', 'sale.order.line', 'addons/sale_plan_emballage/report/plan_metal.rml', parser=plan, header="external")
report_sxw.report_sxw('report.plan_bois', 'sale.order.line', 'addons/sale_plan_emballage/report/plan_bois.rml', parser=plan, header="external")
report_sxw.report_sxw('report.plan_emballage', 'sale.order.line', 'addons/sale_plan_emballage/report/plan_emballage.rml', parser=plan, header="external")

I have read a lot of tutorials and forum post,but the problem is still there. Odoo says this :

Traceback (most recent call last):
  File "/opt/odoo/odoo-server/addons/report/controllers/main.py", line 116, in report_download
    response = self.report_routes(reportname, docids=docids, converter='pdf')
  File "/opt/odoo/odoo-server/openerp/http.py", line 405, in response_wrap
    response = f(*args, **kw)
  File "/opt/odoo/odoo-server/addons/report/controllers/main.py", line 65, in report_routes
    pdf = report_obj.get_pdf(cr, uid, docids, reportname, data=options_data, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 268, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/addons/report/models/report.py", line 192, in get_pdf
    html = self.get_html(cr, uid, ids, report_name, data=data, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 268, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/addons/report/models/report.py", line 177, in get_html
    return self.render(cr, uid, [], report.report_name, docargs, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 268, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/addons/report/models/report.py", line 153, in render
    return view_obj.render(cr, uid, template, values, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 268, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 1022, in render
    return self.pool[engine].render(cr, uid, id_or_xml_id, qcontext, loader=loader, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 268, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 263, in render
    return self.render_node(self.get_template(id_or_xml_id, qwebcontext), qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 302, in render_node
    result = self.render_element(element, template_attributes, generated_attributes, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 323, in render_element
    g_inner.append(self.render_node(current_node, qwebcontext))
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 300, in render_node
    result = self._render_tag[t_render](self, element, template_attributes, generated_attributes, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 438, in render_tag_call
    d[0] = self.render_element(element, template_attributes, generated_attributes, d)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 323, in render_element
    g_inner.append(self.render_node(current_node, qwebcontext))
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 302, in render_node
    result = self.render_element(element, template_attributes, generated_attributes, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 323, in render_element
    g_inner.append(self.render_node(current_node, qwebcontext))
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 302, in render_node
    result = self.render_element(element, template_attributes, generated_attributes, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 323, in render_element
    g_inner.append(self.render_node(current_node, qwebcontext))
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 300, in render_node
    result = self._render_tag[t_render](self, element, template_attributes, generated_attributes, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 375, in render_tag_esc
    inner = widget.format(template_attributes['esc'], options, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 1000, in format
    return escape(self._format(inner, options, qwebcontext))
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 997, in _format
    return self.pool['ir.qweb'].eval_str(inner, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 215, in eval_str
    val = self.eval(expr, qwebcontext)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 207, in eval
    raise_qweb_exception(message="Could not evaluate expression %r" % expr, expression=expr, template=template)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 204, in eval
    return qwebcontext.safe_eval(expr)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 89, in safe_eval
    return eval(expr, None, locals_dict, nocopy=True, locals_builtins=True)
  File "/opt/odoo/odoo-server/openerp/tools/safe_eval.py", line 314, in safe_eval
    return eval(c, globals_dict, locals_dict)
  File "", line 1, in <module>
QWebException: "'NoneType' object is not callable" while evaluating
'hello_world()'

I think i have correctly configure the parser. Any suggestions ?