[Checkins] [zopefoundation/Zope] 87abba: Use DocumentTemplate branch 3.x. (#889)

[Maurits van Rees]

  Branch: refs/heads/4.x
  Home:   https://github.com/zopefoundation/Zope
  Commit: 87abba709b2a2edf25ef2bd2bbffdc71b895197f
      https://github.com/zopefoundation/Zope/commit/87abba709b2a2edf25ef2bd2bbffdc71b895197f
  Author: Maurits van Rees <m.van.rees at zestsoftware.nl>
  Date:   2020-09-17 (Thu, 17 Sep 2020)

  Changed paths:
    M sources.cfg

  Log Message:
  -----------
  Use DocumentTemplate branch 3.x. (#889)

The master branch targets Zope 5.
It fails with python 2.7:

```
File "/Users/maurits/community/plone-coredev/5.2/src/DocumentTemplate/src/DocumentTemplate/DT_Var.py", line 156, in <module>
    import urllib.parse
ImportError: No module named parse
```