[ADD] Support for --upgrade-path

[StefanRijnhart]

Adapting load_data to search for the file to load in the --upgrade-path if it cannot be found in the module directory tree.

[legalsylvain]

thanks.

[StefanRijnhart]

Thanks for the reviews. I noticed a slight logical error that I just fixed

+++ b/openupgradelib/openupgrade.py
@@ -278,7 +278,9 @@ def load_data(cr, module_name, filename, idref=None, mode='init'):
         if tools.config.get('upgrade_path'):
             pathname = os.path.join(
                 tools.config['upgrade_path'], module_name, filename)
-        fp = open(pathname)
+            fp = open(pathname)
+        else:
+            raise
 
     try:
         if ext == '.csv':