Hello while i was trying to install a module purchase request i got this error can anyone help with a solution to this thanks ?

Odoo Server ErrorTraceback (most recent call last): File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/http.py", line 643, in _handle_exception return super(JsonRequest, self)._handle_exception(exception) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/http.py", line 680, in dispatch result = self._call_function(**self.params) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/http.py", line 316, in _call_function return checked_call(self.db, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/service/model.py", line 118, in wrapper return f(dbname, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/http.py", line 309, in checked_call result = self.endpoint(*a, **kw) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/http.py", line 959, in __call__ return self.method(*args, **kw) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/http.py", line 509, in response_wrap response = f(*args, **kw) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/web/controllers/main.py", line 896, in call_button action = self._call_kw(model, method, args, {}) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/web/controllers/main.py", line 884, in _call_kw return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/module/module.py", line 459, in button_immediate_install return self._button_immediate_function(cr, uid, ids, self.button_install, context=context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/module/module.py", line 533, in _button_immediate_function registry = openerp.modules.registry.RegistryManager.new(cr.dbname, update_module=True) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/modules/registry.py", line 386, in new openerp.modules.load_modules(registry._db, force_demo, status, update_module) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/modules/loading.py", line 338, in load_modules loaded_modules, update_module) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/modules/loading.py", line 237, in load_marked_modules loaded, processed = load_module_graph(cr, graph, progressdict, report=report, skip_modules=loaded_modules, perform_checks=perform_checks) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/modules/loading.py", line 156, in load_module_graph _load_data(cr, module_name, idref, mode, kind='data') File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/modules/loading.py", line 98, in _load_data tools.convert_file(cr, module_name, filename, idref, mode, noupdate, kind, report) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/tools/convert.py", line 851, in convert_file convert_xml_import(cr, module, fp, idref, mode, noupdate, report) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/tools/convert.py", line 938, in convert_xml_import obj.parse(doc.getroot(), mode=mode) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/tools/convert.py", line 801, in parse self.parse(rec, mode) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/tools/convert.py", line 804, in parse self._tags[rec.tag](self.cr, rec, de, mode=mode) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/tools/convert.py", line 708, in _tag_record id = self.pool['ir.model.data']._update(cr, self.uid, rec_model, self.module, res, rec_id or False, not self.isnoupdate(data_node), noupdate=self.isnoupdate(data_node), mode=self.mode, context=rec_context ) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/ir/ir_model.py", line 1142, in _update res_id = model_obj.create(cr, uid, values, context=context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/res/res_users.py", line 746, in create res = super(groups_view, self).create(cr, uid, values, context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/res/res_users.py", line 638, in create self.write(cr, uid, [gid], {'users': users}, context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 381, in old_api result = method(recs, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/mail/models/res_users.py", line 147, in write write_res = super(res_groups_mail_channel, self).write(vals) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 248, in wrapper return new_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 574, in new_api result = method(self._model, cr, uid, self.ids, *args, **old_kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/res/res_users.py", line 753, in write res = super(groups_view, self).write(cr, uid, ids, values, context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/res/res_users.py", line 642, in write res = super(groups_implied, self).write(cr, uid, ids, values, context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/base/res/res_users.py", line 118, in write res = super(res_groups, self).write(cr, uid, ids, vals, context=context) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 250, in wrapper return old_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 381, in old_api result = method(recs, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/models.py", line 3837, in write self._write(old_vals) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 248, in wrapper return new_api(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/api.py", line 574, in new_api result = method(self._model, cr, uid, self.ids, *args, **old_kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/models.py", line 3988, in _write result += self._columns[field].set(cr, self, id, field, vals[field], user, context=rel_context) or [] File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/osv/fields.py", line 1070, in set link([act[1]]) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/osv/fields.py", line 1045, in link cr.execute(query, (id, list(sub_ids), id)) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/sql_db.py", line 141, in wrapper return f(self, *args, **kwargs) File "/opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/sql_db.py", line 220, in execute res = self._obj.execute(query, params)ParseError: "insert or update on table "res_groups_users_rel" violates foreign key constraint "res_groups_users_rel_uid_fkey"DETAIL: Key (uid)=(4) is not present in table "res_users". " while parsing /opt/bitnami/apps/odoo/lib/odoo-9.0rc20160415-py2.7.egg/openerp/addons/purchase_request/security/purchase_request.xml:13, near<record id="group_purchase_request_user" model="res.groups"> <field name="name">Purchase Request User</field> <field name="users" eval="[(4, ref('base.group_user'))]"/> <field name="category_id" ref="module_category_purchase_request"/> </record>