Add mitmproxy for openstack/mitmstack

- Is the library actively maintained?

Yes, see activities during last month[1] and releases[2]

- Is the library good code?

Yes, see building history[3] and test coverage[4]

- Is the library python 3 compatible?

Yes, it is py35 and py36 compatible[5]

- Is the library license compatible?

Yes, MIT[6]

- Is the library already packaged in the distros we target
(Ubuntu latest / Fedora latest)?

No

- Is the function of this library already covered by other
libraries in global-requirements.txt?

No

- Is the library required for OpenStack project or related
dev or infrastructure setup? (Answer to this should be Yes,
of course) Which?

Yes, mitmproxy[7] is used by openstack/mitmstack[8] for
intercepting, inspecting, modifying and replaying traffic flows.

[1]: https://github.com/mitmproxy/mitmproxy/pulse/monthly
[2]: https://github.com/mitmproxy/mitmproxy/releases
[3]: https://travis-ci.org/mitmproxy/mitmproxy/builds
[4]: https://codecov.io/gh/mitmproxy/mitmproxy
[5]: https://pypi.python.org/pypi/mitmproxy
[6]: https://github.com/mitmproxy/mitmproxy/blob/master/LICENSE
[7]: https://mitmproxy.org/
[8]: https://wiki.openstack.org/wiki/MitmStack

Change-Id: I9893cb08019938e025b8e1c60dca6fbdb7e95ce2

global-requirements.txt

@@ -100,6 +100,7 @@ Mako>=0.4.0  # MIT
 marathon>=0.8.6  # MIT
 microversion-parse>=0.1.2  # Apache-2.0
 mistral!=2015.1.0,>=3.0.0  # Apache-2.0
+mitmproxy>=1.0.2;python_version>'3.0'  # MIT
 monasca-common>=1.4.0  # Apache-2.0
 monasca-statsd>=1.1.0  # Apache-2.0
 monotonic>=0.6                          # Apache-2.0

upper-constraints.txt

@@ -189,6 +189,7 @@ lxml===3.7.2
 marathon===0.8.10
 microversion-parse===0.1.4
 mistral===3.0.2
+mitmproxy===1.0.2;python_version>'3.0'
 mock===2.0.0
 monasca-common===1.4.0
 monasca-statsd===1.5.0