Bug 1493997: [mozharness] Ensure that MOZ_TOOLCHAINS isn't specified if mach isn't available; r=ahal

Differential Revision: https://phabricator.services.mozilla.com/D6800

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

testing/mozharness/mozharness/mozilla/tooltool.py

@@ -18,6 +18,7 @@ _here = os.path.abspath(os.path.dirname(__file__))
 _external_tools_path = os.path.normpath(os.path.join(_here, '..', '..',
                                                      'external_tools'))
 
+
 class TooltoolMixin(object):
     """Mixin class for handling tooltool manifests.
     To use a tooltool server other than the Mozilla server, override
@@ -91,6 +92,10 @@ class TooltoolMixin(object):
 
         toolchains = os.environ.get('MOZ_TOOLCHAINS')
         if toolchains:
+            if not self.topsrcdir:
+                raise Exception(
+                    'MOZ_TOOLCHAINS is not supported for tasks without '
+                    'a source checkout.')
             cmd.extend(toolchains.split())
 
         timeout = self.config.get('tooltool_timeout', 10 * 60)

tools/lint/flake8.yml

@@ -40,6 +40,7 @@ flake8:
         - testing/mozharness/mozharness/mozilla/l10n/locales.py
         - testing/mozharness/mozharness/mozilla/mar.py
         - testing/mozharness/mozharness/mozilla/testing/
+        - testing/mozharness/mozharness/mozilla/tooltool.py
         - testing/mozharness/mozinfo
         - testing/mozharness/scripts
         - testing/raptor