Ignore new error that we didn't enforced before.

theano/tests/test_flake8.py

@@ -38,7 +38,7 @@ __contact__ = "Saizheng Zhang <saizhenglisa..at..gmail.com>"
 # - "ambiguous variable name" (E741)
 #   Redundant error code generated by flake8-future-import module
 ignore = ('E501', 'E123', 'E133', 'FI12', 'FI14', 'FI15', 'FI16', 'FI17',
-          'FI50', 'FI51', 'FI53', 'E305', 'E741')
+          'FI18', 'FI50', 'FI51', 'FI53', 'E305', 'E741')
 
 whitelist_flake8 = [
     "__init__.py",