test_subprocess was failing for me on my laptop, and my laptop only.  With some guidance from haypo on using strace, I tracked the problem down to the fact that the last directory in my path is a directory to which I don't have permission.  So the error subprocess was getting from trying to access the non-existent file was "permission denied" (errno 13) instead of not found (errno 2).

It is possible this is an error in subprocess as well, since the shell, for example, returns command not found in that case.  But I don't think that it is, since I think the errno is being returned by the exec call.  So, I think the test just needs to be changed to ignore errno 13 as well (by name, of course).

New changeset 2b75ac7c9c12 by R David Murray in branch '3.1':
#11490: EACCES can also mean command not found
http://hg.python.org/cpython/rev/2b75ac7c9c12

New changeset 67f4ef6094ed by R David Murray in branch '3.2':
Merge fix for #11490 from 3.1.
http://hg.python.org/cpython/rev/67f4ef6094ed

New changeset cdfdc99d21d3 by R David Murray in branch 'default':
Merge fix for #11490 from 3.2.
http://hg.python.org/cpython/rev/cdfdc99d21d3

New changeset 0a19b3278fa2 by R David Murray in branch '2.7':
#11490: EACCES can also mean command not found
http://hg.python.org/cpython/rev/0a19b3278fa2