That looks like a bug in dateutil? (the exception is raised while trying to format the message for the actual exception...) Let's see whether @pganssle plans to fix that soon, if there's an (e.g.) 2.8.1.1 that fixes it perhaps we can just not support 2.8.1.

I don't think this has been reported, do you have any details about how to trigger this?

traceback is at #15726, sorry I don't have a minimal repro but the last line of the tb is

~/anaconda3/envs/pylandstats/lib/python3.6/site-packages/dateutil/parser/_parser.py in parse(self, timestr, default, ignoretz, tzinfos, **kwargs)
    655             ret = self._build_naive(res, default)
    656         except ValueError as e:
--> 657             six.raise_from(ParserError(e.args[0] + ": %s", timestr), e)
    658 
    659         if not ignoretz:

TypeError: unsupported operand type(s) for +: 'int' and 'str'

Created an issue in dateutil/dateutil#981.

Shouldn't be too tough to fix it.

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout v2.2.x
$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 026dacd2cb90dc6b2cf17a8edafda213f51cb7c6

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am 'Backport PR #15729: Catch correct parse errror type for dateutil >= 2.8.1'

4. Push to a named branch :

git push YOURFORK v2.2.x:auto-backport-of-pr-15729-on-v2.2.x

5. Create a PR against branch v2.2.x, I would have named this PR:

"Backport PR #15729 on branch v2.2.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to suggest an improvement.

Doesn't need backport to 2.2.x because that code path did not exist there yet.