Implement workaround for login error.

[xperimental]

This contains the workaround mentioned by @cuibonobo. I have manually applied it to my Synapse instance and it seems to work.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file
• Pull request includes a sign off

[codecov-io]

Codecov Report

Merging #4486 into develop will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #4486      +/-   ##
===========================================
- Coverage    74.67%   74.67%   -0.01%     
===========================================
  Files          336      336              
  Lines        34293    34293              
  Branches      5592     5592              
===========================================
- Hits         25610    25609       -1     
- Misses        7096     7099       +3     
+ Partials      1587     1585       -2

[xperimental]

I noticed that the linter was complaining about the length of the line. Having not done much Python before, I'd appreciate feedback on whether breaking the line with a backslash is the preferred way to achieve the result.

[richvdh]

Having not done much Python before, I'd appreciate feedback on whether breaking the line with a backslash is the preferred way to achieve the result.

It's a subjective choice. We normally use parens here:

if (self.parent_context is not None
    and hasattr(self.parent_context, '_resource_usage')
):
    # do some stuff

or something like that.

(see also https://github.com/matrix-org/synapse/blob/master/docs/code_style.rst)

[xperimental]

Thanks @richvdh . I have updated the code to reflect the other code style.

[richvdh]

Thanks!