Return both stdout and stderr on pip failures.

pip failure message sometimes (always?) go to standard out. Return
both standard out and standard error when there's a failure.

library/pip

@@ -178,7 +178,13 @@ def main():
             err += err_pip
 
     if rc != 0:
-        module.fail_json(msg=err, cmd=cmd)
+        if not out:
+            msg = err
+        elif not err:
+            msg = out
+        else:
+            msg = "stdout: %s\n:stderr: %s" % (out, err)
+        module.fail_json(msg=msg, cmd=cmd)
 
     module.exit_json(changed=changed, cmd=cmd, name=name, version=version,
                      state=state, requirements=requirements, virtualenv=env)