Bug 1471920 - [mozbuild] Use shutil.which in Python 3 instead of vendored third-party package r=davehunt

Use shutil.which in mozbuild for Python 3 instead of vendored third-party package, and enable mozversion tests that are fixed under Python 3 by this change.

Differential Revision: https://phabricator.services.mozilla.com/D4184

--HG--
extra : moz-landing-system : lando

python/mozbuild/mozbuild/base.py

@@ -11,6 +11,10 @@ import multiprocessing
 import os
 import subprocess
 import sys
+try:
+    from shutil import which
+except ImportError:
+    # shutil.which is not available in Python 2.7
     import which
 
 from mach.mixin.process import ProcessExecutionMixin

testing/mozbase/mozversion/tests/manifest.ini

@@ -1,5 +1,6 @@
 [DEFAULT]
 subsuite = mozbase, os == "linux"
-skip-if = python == 3
+
 [test_binary.py]
 [test_apk.py]
+skip-if = python == 3