Update tox.ini
add E741 and F541 to flake8 ignore list so TravisCI linting doesn't fail
@@ -53,6 +53,7 @@ ignore =
E712, # comparison to True should be 'if cond is True:' or 'if cond:'
E713, # test for membership should be 'not in'
E722, # do not use bare 'except'
+ E741, # ambiguous variable name
F401, # '<module>' imported but unused
F403, # 'from <module> import *' used; unable to detect undefined names
F405, # '<name>' may be undefined, or defined from star imports
@@ -98,6 +99,7 @@ ignore =
E701, # multiple statements on one line (colon)
E704, # multiple statements on one line (def)
E731, # do not assign a lambda expression, use a def
+ F541, # f-string is missing placeholders
W191, # indentation contains tabs
W291, # trailing whitespace
W293, # blank line contains whitespace
