Transient Windows test failures

[Matt Harbison]

On Fri, 16 Jun 2017 09:59:30 -0400, Augie Fackler <raf at durin42.com> wrote:

> On Fri, Jun 16, 2017 at 12:18:18AM -0400, Matt Harbison wrote:
>> So apparently, this is a symptom of not having %SystemRoot% in the
>> environment when calling CreateProcess().
>>
>> https://bugs.python.org/issue13524
>> https://jpassing.com/2009/12/28/the-hidden-danger-of-forgetting-to-specify-systemroot-in-a-custom-environment-block/
>>
>> I see that setup.py special cases this variable.  I did a search for  
>> 'env
>> =', and it looks like hooks and pager start with empty environments, so  
>> they
>> must not inherit this.  IDR if any recent changes were made that start  
>> with
>> an empty environment.
>>
>> The thing I can't get my mind around is the hit and miss nature of the
>> error, if this is really the problem.
>
> It sounds like it should be harmless to just always forward
> %SystemRoot% - should we just do that?

Seems reasonable, but run-tests._getenv() already does an  
os.environ.copy(), so it should be there?

It does seem like a good idea to do it for hooks and other things  
executed, where the environment is built from scratch.  The question is  
where?  There's util.popen[2-4](), plus some direct calls to  
subprocess.Popen(), and an os.system().  I considered util.shellenviron(),  
but there are far fewer calls to this than places where processes are  
spawned.

I just hit it here:

--- c:/Users/Matt/projects/hg/tests/test-log.t
+++ c:/Users/Matt/projects/hg/tests/test-log.t.err
@@ -1476,72 +1476,64 @@
    $ hg resolve -m foo
    (no more unresolved files)
    $ hg ci -m "First merge, related"
+  abort: Invalid Signature
+  [255]

I was wondering if it's right on the edge of some limit, and paths or  
whatever being set by the test runner are (sometimes) pushing it out of  
the environment block.  But the docs say there's no limit to the block  
size:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms682653(v=vs.85).aspx

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