protect import of external dependencies

Odoo won't install an addon if the external dependencies are not met.
However, the python modules of the addons are imported at startup, and the
lack of an external dependency for an external addon will cause a crash,
therefore the import needs to be in a try..except block.

account_banking_pain_base/models/banking_export_pain.py

@@ -24,12 +24,17 @@ from openerp.osv import orm
 from openerp.tools.translate import _
 from openerp.tools.safe_eval import safe_eval
 from datetime import datetime
-from unidecode import unidecode
 from lxml import etree
 from openerp import tools
 import logging
 import base64
 
+
+try:
+    from unidecode import unidecode
+except ImportError:
+    unidecode = None
+
 logger = logging.getLogger(__name__)