pywikibot has had special support for SVN version 1.6 and earlier, by manually parsing the SVN undocumented entries file (version 11 or earlier).
getversion_svn in the first revision (82d7a63) of core's version.py parsed entries and returned a formatted tag using
tag = '[%s] %s' % (t[0], t[1])
79843a6 (https://gerrit.wikimedia.org/r/#/c/86375/ - Feb 2014) then used this tag value in a URL to github.com to obtain a hash, resulting in an error from github, and an exception in Python. tag was updated for SVN v1.7+, but not v1.6 and earlier.
(after creating a .svn/entries in the version 10 file format)
core$ python pwb.py shell Welcome to the Pywikibot interactive shell! >>> import pywikibot >>> pywikibot.version.getversion_svn() WARNING: Http response status 400 Traceback (most recent call last): File "<console>", line 1, in <module> File ".../pywikibot/version.py", line 184, in getversion_svn hsh = github_svn_rev2hash(tag, rev) File ".../pywikibot/version.py", line 166, in github_svn_rev2hash dom = xml.dom.minidom.parse(StringIO(data)) File "/usr/lib64/python2.7/xml/dom/minidom.py", line 1921, in parse return expatbuilder.parse(file) File "/usr/lib64/python2.7/xml/dom/expatbuilder.py", line 928, in parse result = builder.parseFile(file) File "/usr/lib64/python2.7/xml/dom/expatbuilder.py", line 207, in parseFile parser.Parse(buffer, 0) ExpatError: undefined entity: line 13, column 20
(the same bug appears in compat.)