Fix error messages for host not found when host is passed in as bytes

[ncollins]

open_tcp_stream can take host as either bytes or str, but the formatting for the error message when a host is not found depends on host being a string. When trying to connect to a non-existent host, if passed as a string I would get the exception:

OSError: all attempts to connect to localhost:8081 failed

but when passed as bytes I would get the exception:

if ":" in host:

TypeError: a bytes-like object is required, not 'str'

This PR adds a single line to convert bytes to a string before running the rest of the function (and some tests).

[njsmith]

Nice catch!

The test failure is #624, nothing to worry about here.

The one thing that jumped out at me is that the interaction of hostnames and text encoding is stupidly complicated. So is a plain .decode() the right thing to do? On Python 2 that meant "use some random system-defined text encoding", which is definitely not right, but it looks like on Python 3 they made it so plain .decode() always uses utf-8, which is less wrong... but still probably wrong, because when a hostname is passed as bytes, we assume that it's already in the standard hostname "A-label" form, which is required to be all-ascii. Also, for hostnames we guarantee that bytes and str representations behave identically if they're all ascii, but for non-ascii characters idna gets involved and who knows what that even does.

So I think the right thing to do here is .decode("ascii"). Can you make that change?

And finally, can you add a newsfragment? Just create a file called newsfragments/633.bugfix.rst, and put a brief description of what was fixed.

[codecov]

Codecov Report

Merging #633 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #633      +/-   ##
==========================================
+ Coverage   99.28%   99.28%   +<.01%     
==========================================
  Files          91       91              
  Lines       10763    10767       +4     
  Branches      768      768              
==========================================
+ Hits        10686    10690       +4     
  Misses         58       58              
  Partials       19       19

Impacted Files	Coverage Δ
trio/_highlevel_open_tcp_stream.py	96.92% <100%> (+0.04%)	⬆️
trio/tests/test_highlevel_open_tcp_stream.py	100% <100%> (ø)	⬆️

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[ncollins]

Thanks for the help. I've made those changes.

[njsmith]

Awesome, thanks! Merging now 🎉 🎂 And, no pressure, but if you'd like to keep contributing then we'd love to have you, so I'm also sending you a github invite. You can read more about this in our contributing documentation.