I am using V7 on Ubuntun 12.10

I created a custom module creating a new product object that extends product.product with one field and successfully installed it. I would like to uninstall it and re-install it again to make sure everything is allright.

When uninstalling, I have the following error : No such external ID currently defined in the system: product.cat1

Below the full error message and my code

Client Traceback (most recent call last):
  File "/opt/openerp/server/openerp/addons/web/http.py", line 195, in dispatch
    response["result"] = method(self, **self.params)
  File "/opt/openerp/server/openerp/addons/web/controllers/main.py", line 1082, in call_button
    action = self._call_kw(req, model, method, args, {})
  File "/opt/openerp/server/openerp/addons/web/controllers/main.py", line 1070, in _call_kw
    return getattr(req.session.model(model), method)(*args, **kwargs)
  File "/opt/openerp/server/openerp/addons/web/session.py", line 43, in proxy
    result = self.proxy.execute_kw(self.session._db, self.session._uid, self.session._password, self.model, method, args, kw)
  File "/opt/openerp/server/openerp/addons/web/session.py", line 31, in proxy_method
    result = self.session.send(self.service_name, method, *args)
  File "/opt/openerp/server/openerp/addons/web/session.py", line 104, in send
    raise xmlrpclib.Fault(openerp.tools.exception_to_unicode(e), formatted_info)


Server Traceback (most recent call last):
  File "/opt/openerp/server/openerp/addons/web/session.py", line 90, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/opt/openerp/server/openerp/netsvc.py", line 289, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/opt/openerp/server/openerp/service/web_services.py", line 614, in dispatch
    res = fn(db, uid, *params)
  File "/opt/openerp/server/openerp/osv/osv.py", line 169, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/opt/openerp/server/openerp/osv/osv.py", line 123, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/opt/openerp/server/openerp/osv/osv.py", line 179, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/opt/openerp/server/openerp/osv/osv.py", line 166, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/opt/openerp/server/openerp/addons/base/module/module.py", line 496, in button_immediate_uninstall
    return self._button_immediate_function(cr, uid, ids, self.button_uninstall, context=context)
  File "/opt/openerp/server/openerp/addons/base/module/module.py", line 476, in _button_immediate_function
    _, pool = pooler.restart_pool(cr.dbname, update_module=True)
  File "/opt/openerp/server/openerp/pooler.py", line 39, in restart_pool
    registry = RegistryManager.new(db_name, force_demo, status, update_module)
  File "/opt/openerp/server/openerp/modules/registry.py", line 214, in new
    openerp.modules.load_modules(registry.db, force_demo, status, update_module)
  File "/opt/openerp/server/openerp/modules/loading.py", line 349, in load_modules
    processed = load_marked_modules(cr, graph, states_to_load, force, status, report, loaded_modules, update_module)
  File "/opt/openerp/server/openerp/modules/loading.py", line 260, in load_marked_modules
    loaded, processed = load_module_graph(cr, graph, progressdict, report=report, skip_modules=loaded_modules, perform_checks=perform_checks)
  File "/opt/openerp/server/openerp/modules/loading.py", line 195, in load_module_graph
    load_demo_xml(module_name, idref, mode)
  File "/opt/openerp/server/openerp/modules/loading.py", line 76, in <lambda>
    load_demo_xml = lambda *args: _load_data(cr, *args, kind='demo_xml')
  File "/opt/openerp/server/openerp/modules/loading.py", line 128, in _load_data
    tools.convert_xml_import(cr, module_name, fp, idref, mode, noupdate, report)
  File "/opt/openerp/server/openerp/tools/convert.py", line 954, in convert_xml_import
    obj.parse(doc.getroot())
  File "/opt/openerp/server/openerp/tools/convert.py", line 847, in parse
    self._tags[rec.tag](self.cr, rec, n)
  File "/opt/openerp/server/openerp/tools/convert.py", line 805, in _tag_record
    f_val = self.id_get(cr, f_ref)
  File "/opt/openerp/server/openerp/tools/convert.py", line 824, in id_get
    res = self.model_id_get(cr, id_str)
  File "/opt/openerp/server/openerp/tools/convert.py", line 833, in model_id_get
    return model_data_obj.get_object_reference(cr, self.uid, mod, id_str)
  File "/opt/openerp/server/openerp/tools/cache.py", line 18, in lookup
    r = self.lookup(self2, cr, *args)
  File "/opt/openerp/server/openerp/tools/cache.py", line 46, in lookup
    value = d[key] = self.method(self2, cr, *args)
  File "/opt/openerp/server/openerp/addons/base/ir/ir_model.py", line 861, in get_object_reference
    data_id = self._get_id(cr, uid, module, xml_id)
  File "/opt/openerp/server/openerp/tools/cache.py", line 18, in lookup
    r = self.lookup(self2, cr, *args)
  File "/opt/openerp/server/openerp/tools/cache.py", line 46, in lookup
    value = d[key] = self.method(self2, cr, *args)
  File "/opt/openerp/server/openerp/addons/base/ir/ir_model.py", line 854, in _get_id
    raise ValueError('No such external ID currently defined in the system: %s.%s' % (module, xml_id))
ValueError: No such external ID currently defined in the system: product.cat1

My file : __openerp__.py

{
        "name" : "Products Apparel Syang",
        "version" : "1.0",
        "author" : "Syang",
        "category" : "Generic Modules/Inventory Control",
        "description": "Add a field to product to handle color and size",
        "depends" : ["product"],
        "init_xml" : [],
        "demo_xml" : [],
        "update_xml" : [],
        "installable": True,
        "active": False
}

My file : product_apparel_syang.py :

from osv import fields, osv
class product_apparel_syang(osv.osv):
        _name = "product.apparel.syang"
        _inherit = "product.product"
        _description = "Add colors and size property to a product"
        _columns = {
                'product_color' : fields.integer('Product', help="color of the product")
        }
product_apparel_syang()