Enable E128 ignore E129

After bumping the hacking version to the 0.9.x series ignores were
added for several rules. This commit fixes the violations for a subset
of these rules and re-enables the checks.

Change-Id: Iaff25fc9e2ecfad0c0574b39ddce0c5188d6c31f

tempest/exceptions.py

@@ -224,4 +224,7 @@ class CommandFailed(Exception):
     def __str__(self):
         return ("Command '%s' returned non-zero exit status %d.\n"
                 "stdout:\n%s\n"
-        "stderr:\n%s" % (self.cmd, self.returncode, self.stdout, self.stderr))
+                "stderr:\n%s" % (self.cmd,
+                                 self.returncode,
+                                 self.stdout,
+                                 self.stderr))