test: support python >= 3.6

on python3.6, subprocess error message is different, use a
zope.testing.renormalizing rule to normalize the message.

slapos/recipe/cmmi/README.rst

@@ -1057,7 +1057,7 @@ developer can try same build process as the recipe tried.
     Installing package.
     package: Checking whether package is installed at shared path: /shared/package/FIRST_SHARED_PACKAGE_HASH
     package: [ENV] FOO = bar
-    package: Command './configure --prefix="/shared/package/FIRST_SHARED_PACKAGE_HASH"' returned non-zero exit status 127
+    package: Command './configure --prefix="/shared/package/FIRST_SHARED_PACKAGE_HASH"' returned non-zero exit status 127.
     package: Compilation error. The package is left as is at /shared/package/FIRST_SHARED_PACKAGE_HASH__compile__ where you can inspect what went wrong.
     A shell script slapos.recipe.build.env.sh has been generated. You can source it in your shell to reproduce build environment.
     /bin/sh: 1: ./configure: not found

slapos/recipe/cmmi/tests.py

@@ -357,6 +357,10 @@ def test_suite():
                 signature_FIRST_SHARED_PACKAGE_HASH.hexdigest()),
                (re.compile('ANOTHER_SHARED_PACKAGE_HASH'),
                 signature_ANOTHER_SHARED_PACKAGE_HASH.hexdigest()),
+                # Normalize subprocess.CalledProcessError message, on python >= 3.6
+                # there's an extra . at the end.
+               (re.compile(r'Command (.*) returned non-zero exit status (\d+)[\.]{0,1}'),
+                  r'Command \1 returned non-zero exit status \2.'),
                 zc.buildout.testing.normalize_path,
                 zc.buildout.testing.not_found,
             ]),