[IMP] Soft fail on missing cups import

cups is an external dependency, if it is not installed Odoo will not start.
OCA guidelines specify guidelines for External dependencies, code is from there.

base_report_to_printer/wizard/update_printers.py

@@ -21,13 +21,18 @@
 #
 ##############################################################################
 
-import cups
+import logging
+_logger = logging.getLogger(__name__)
+
+try:
+    import cups
+except ImportError:
+    _logger.debug('Cannot `import cups`.')
+
 from openerp.exceptions import Warning
 from openerp import models, api, _
 from openerp.tools.config import config
-import logging
 
-_logger = logging.getLogger(__name__)
 CUPS_HOST = config.get('cups_host', 'localhost')
 CUPS_PORT = int(config.get('cups_port', 631))