git commands with Python

Question

Please help. I run a git command and want to read output.

p = subprocess.Popen(['git', 'fetch'],
                 env=os.environ,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
                 cwd="path to repo",
                 universal_newlines=True)

outs, errs = p.communicate()
rcode = p.returncode

I got output:
rcode 0
outs ""
errs *From bitbucket.org:myname/project0\n * [new branch] fetch_out -> program/fetch_out\n*

The command has been finished correct.
Why message has been send to stderr ? I expect on stdout.