Comment 8 for bug 1803558

Please could the fix be baackported to bionic? It stops backportpackage from working:

```
backportpackage lazr.restfulclient -u ppa:christopher-hoskin/ppa -b
Traceback (most recent call last):
  File "/usr/bin/backportpackage", line 31, in <module>
    from ubuntutools.archive import (SourcePackage, DebianSourcePackage,
  File "/usr/lib/python2.7/dist-packages/ubuntutools/archive.py", line 51, in <module>
    from ubuntutools.lp.lpapicache import (Launchpad, Distribution,
  File "/usr/lib/python2.7/dist-packages/ubuntutools/lp/lpapicache.py", line 35, in <module>
    from launchpadlib.launchpad import Launchpad as LP
  File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 38, in <module>
    from lazr.restfulclient.resource import (
  File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/resource.py", line 68, in <module>
    from lazr.restfulclient._browser import Browser, RestfulHttp
  File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 85, in <module>
    from httplib2 import _md5, re_url_scheme, re_slash
ImportError: cannot import name re_slash
```