Bug 1213816 - Properly set OS properties on Arch; r=gps

--HG--
extra : commitid : BRWaT1v7ALL
extra : amend_source : 8def33528465d649dd822414578f18b1bee94f6d

testing/mozbase/mozinfo/mozinfo/mozinfo.py

@@ -90,6 +90,16 @@ elif system == "Linux":
     if not processor:
         processor = machine
     version = "%s %s" % (distro, os_version)
+
+    # Bug in Python 2's `platform` library:
+    # It will return a triple of empty strings on Arch.
+    # It works on Python 3. If we don't have an OS version,
+    # the unit tests fail to run.
+    if not os_version and "ARCH" in release:
+        distro = 'arch'
+        version = release
+        os_version = release
+
     info['os'] = 'linux'
     info['linux_distro'] = distro
 elif system in ['DragonFly', 'FreeBSD', 'NetBSD', 'OpenBSD']: