SourceTree 1.9.6.1 w/ embedded mercurial 3.9.1 - hg flow broken - cannot push changes to server

Since the built-in editor hoses preformatted, a Markdown of this report is at https://gist.github.com/jpluimers/7b0f0b47b6e8f26b09f6f617fdda4d75

Push with embedded mercurial fails indicating hg flow is broken.

hg push --new-branch default

When doing the same command from the console it works fine.

Marked critical as it means I cannot use my normal workflow any more.

Probably means the embedded hg is hosed.

Please try to reproduce and when it fails: provide steps to remove/reinstall the embedded mercurial.

Steps to reproduce:

1. create new hg flow branch
2. make modifications
3. commit
4. push

These were the changes to be pushed:

https://www.dropbox.com/s/o7issos4bhi3bc8/Screenshot%202016-09-12%2010.48.46.png?dl=0 (also attached)

Embedded mercurial:

hg push --new-branch default
pushing to https://jeroenp@bitbucket.org/jeroenp/libssh2-delphi
searching for changes
** Unknown exception encountered with possibly-broken third-party extension hgflow
** which supports versions unknown of Mercurial.
** Please disable hgflow and try your action again.
** If that fixes the bug please report it to the extension author.
** Python 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:24:40) [MSC v.1500 64 bit (AMD64)]** Mercurial Distributed SCM (version 3.9.1)
** Extensions loaded: rebase, transplant, extdiff, fetch, strip, mq, hgflow, sourcetree_auth, shelve  
Traceback (most recent call last):
{{ File "hg", line 45, in <module>}}
{{ File "mercurial\dispatch.pyc", line 59, in run}}File "mercurial\dispatch.pyc", line 125, in dispatch
{{ File "mercurial\dispatch.pyc", line 204, in _runcatch}}
{{ File "mercurial\dispatch.pyc", line 880, in _dispatch}}
{{ File "mercurial\dispatch.pyc", line 637, in runcommand}}
{{ File "mercurial\dispatch.pyc", line 1010, in _runcommand}}
{{ File "mercurial\dispatch.pyc", line 971, in checkargs}}
{{ File "mercurial\dispatch.pyc", line 877, in <lambda>}}
{{ File "mercurial\util.pyc", line 1036, in check}}File "mercurial\extensions.pyc", line 210, in closure
{{ File "mercurial\util.pyc", line 1036, in check}}
{{ File "hgext\mq.pyc", line 3539, in mqcommand}}File "mercurial\util.pyc", line 1036, in check
{{ File "mercurial\commands.pyc", line 5972, in push}}
{{ File "mercurial\exchange.pyc", line 447, in push}}
{{ File "mercurial\exchange.pyc", line 921, in _pushchangeset}}File "mercurial\wireproto.pyc", line 420, in unbundle
{{ File "mercurial\httppeer.pyc", line 235, in _callpush}}
{{ File "mercurial\httppeer.pyc", line 206, in _call}}File "mercurial\httppeer.pyc", line 153, in _callstream
{{ File "urllib2.pyc", line 435, in open}}File "urllib2.pyc", line 548, in http_response
{{ File "urllib2.pyc", line 467, in error}}
{{ File "urllib2.pyc", line 407, in _call_chain}}
{{ File "urllib2.pyc", line 909, in http_error_401}}File "mercurial\url.pyc", line 447, in http_error_auth_reqed
{{ File "C:/Program Files (x86)/Atlassian/SourceTree/extras/hgext/sourcetree_hg_auth.py", line 218, in basic_http_error_auth_reqed}}
{{ return basic_http_error_auth_reqed.orig(self, authreq, host, req, headers)}}
{{ File "urllib2.pyc", line 887, in http_error_auth_reqed}}File "mercurial\url.pyc", line 450, in retry_http_basic_auth
{{ File "C:/Program Files (x86)/Atlassian/SourceTree/extras/hgext/sourcetree_hg_auth.py", line 212, in find_user_password}}
{{ return self._pwd_handler.find_auth(self, realm, authuri, req)}}File "C:/Program Files (x86)/Atlassian/SourceTree/extras/hgext/sourcetree_hg_auth.py", line 103, in find_auth
{{ user, pwd = urllib2.HTTPPasswordMgrWithDefaultRealm.find_user_password(pwmgr, realm, authuri)}}
TypeError: unbound method find_user_password() must be called with HTTPPasswordMgrWithDefaultRealm instance as first argument (got passwordmgr instance instead)             
Completed with errors, see above.

Console::

C:\Users\Developer\Versioned\libssh2-delphi>hg push --new-branch default
pushing to https://jeroenp@bitbucket.org/jeroenp/libssh2-delphi
searching for changes
http authorization required for https://bitbucket.org/jeroenp/libssh2-delphi
realm: Bitbucket.org HTTP
user: jeroenp
password:
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 4 changesets with 19 changes to 15 files