show-tool-versions always reports stdout and stderr encodings as None; remove these reports

[davidsarah]

The stdio output of the show-tool-versions build step always says:

sys.stdout.encoding: None 

sys.stderr.encoding: None 

Note that stdout.encoding and stderr.encoding are None when they are redirected. misc/build_helpers/show-tool-versions.py​ tries to work around that, but fails:

• to get stdout.encoding, it spawns a subprocess in which stdout is not explicitly redirected, which prints its stdout.encoding on stderr.
• to get stderr.encoding, it spawns a subprocess in which stderr is not explicitly redirected, which prints its stderr.encoding on stdout.

This doesn't work because the subprocesses inherit the stdin and stdout that was redirected in their parent. The same happens on a command line, e.g.:

> python -c "import sys, os, subprocess; print subprocess.Popen([sys.executable, '-c', 'import sys;
 print sys.stderr.encoding'], stdin=open(os.devnull), stdout=subprocess.PIPE).communicate()[0]" 2>out.txt
None

[davidsarah]

misc/build_helpers/show-tool-versions.py: remove attempts to show stdout.encoding and stderr.encoding that always printed None due to redirection. Also remove code to show os.path.supports_unicode_filenames which is not useful. refs #1251

[rockstar]

So, we remove the information entirely in this patch. Was the information ever helpful? If not, I'm quite okay with this patch.

If it was helpful, maybe we could check for None and display "redirected" or check sys.stdout.encoding for None and then not print_stderr/print_stdout (because we've already established that it's not helpful when it prints "None") or perhaps print "Redirected" or something like that.

[zooko]

Yes, the information was, as far as I know, never actually produced. Even if I'm wrong and it was, it wasn't important information to us.

[davidsarah]

Replying to zooko:

Yes, the information was, as far as I know, never actually produced.

Correct. Producing it would require ​creating an independent terminal on Unix, or using CreateProcess with bInheritHandles == FALSE on Windows, and that wouldn't justify its complexity here.

[david-sarah@…]

In 3ad08e6d2f7362cf:

misc/build_helpers/show-tool-versions.py: remove attempts to show stdout.encoding and stderr.encoding that always printed None due to redirection. Also remove code to show os.path.supports_unicode_filenames which is not useful. refs #1251