Ignore Flake8 E722

E722 is "do not use bare except", of which we have four violations
in `models/base.py`.

Let's ignore these for now to get the build working again.

tox.ini

@@ -32,7 +32,7 @@ commands = flake8 {posargs}
 
 [flake8]
 exclude = .venv,venv,.tox,dist,doc,build,*.egg,docs,setup.py,*/migrations/
-ignore = E121,E123,E125,E126,E127,E128,E131,E222,E226,E231,E251,E261,E265,E302,E305,E402,E714,F401,F403,F405,F841,W391
+ignore = E121,E123,E125,E126,E127,E128,E131,E222,E226,E231,E251,E261,E265,E302,E305,E402,E714,E722,F401,F403,F405,F841,W391
 max-line-length = 160
 # E121 continuation line under-indented for hanging indent
 # E123 closing bracket does not match indentation of opening bracket's line
@@ -51,6 +51,7 @@ max-line-length = 160
 # E305 expected 2 blank lines after class or function definition, found 1
 # E402 module level import not at top of file
 # E714 test for object identity should be 'is not'
+# E722 do not use bare except
 # F401 Imported but unused
 # F403 'from module import *' used; unable to detect undefined names
 # F405 foo may be undefined, or defined from star imports