Polish quoting

[asvetlov]

Forbid non-strings (integers for example) in url_for parameters.

[codecov-io]

Codecov Report

Merging #2668 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #2668   +/-   ##
=======================================
  Coverage   97.98%   97.98%           
=======================================
  Files          39       39           
  Lines        7246     7246           
  Branches     1257     1258    +1     
=======================================
  Hits         7100     7100           
  Misses         45       45           
  Partials      101      101

Impacted Files	Coverage Δ
aiohttp/web_urldispatcher.py	99.5% <100%> (ø)	⬆️

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[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new