[FIX] product_m2mcategories: product.categ_id is mandatory, else it won't invoice properly. And mandatory fields are advised to stay on the first tab...

Might not look as good, but will work better this way unfortunately...

product_m2mcategories/product.py

@@ -19,7 +19,7 @@ from osv import osv,fields
 class product_product(osv.osv):
     _inherit = "product.template"
     _columns = {
-        'categ_id': fields.many2one('product.category','Pricing/Primary Category',change_default=True),
+        'categ_id': fields.many2one('product.category','Pricing/Primary Category', required=True, change_default=True),
         'categ_ids': fields.many2many('product.category','product_categ_rel','product_id','categ_id','Product Categories')
     }
-product_product()
+product_product()

product_m2mcategories/product_view.xml

@@ -1,16 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <openerp>
     <data>
-        <record id="product_normal_form_view_rem_categid" model="ir.ui.view">
-            <field name="name">product.normal.form</field>
-            <field name="model">product.product</field>
-            <field name="inherit_id" ref="product.product_normal_form_view" />
-            <field name="type">form</field>
-            <field eval="7" name="priority"/>
-            <field name="arch" type="xml">
-                <xpath expr="/form/notebook/page/group/field[@name='categ_id']" position="replace"/>
-            </field>
-        </record>
         <record id="product_normal_form_view_add_categids" model="ir.ui.view">
             <field name="name">product.normal.form</field>
             <field name="model">product.product</field>
@@ -19,9 +9,7 @@
             <field eval="7" name="priority"/>
             <field name="arch" type="xml">
                 <xpath expr="/form/notebook/page[@string='Information']" position="after">
-                    <page string="Categorisation">
-                        <field name="categ_id" colspan="2"/>
-                        <newline/>
+                    <page string="Extra Categories">
                         <separator string="Classification Categories" colspan="2"/>
                         <newline/>
                         <field name="categ_ids" nolabel="1" colspan="2"/>