installation: HTTPretty==0.8.10 version pin
installation: HTTPretty==0.8.10 version pin

* Pins HTTPretty version to 0.8.10 due to broken compatibility with
  Python 3.  (addresses gabrielfalcao/HTTPretty#269)

Signed-off-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio-oauthclient,tiborsimko/invenio-oauthclient,inveniosoftware/invenio-oauthclient,inveniosoftware/invenio-oauthclient,tiborsimko/invenio-oauthclient,inveniosoftware/invenio-oauthclient