Finish Python3 Support

[nmuesch]

What does this PR do?

Finish Py3 support for postgres by only using zip when iterating.

Motivation

ddev validate py3 postgres was failing
PY2 bas the built in zip return the whole iterable, but PY3 returns an iterator.
We were only using the return value once anyway, but this ensures it and makes the validation pass.

Review checklist

• PR has a meaningful title or PR has the no-changelog label attached
• Feature or bugfix has tests
• Git history is clean
• If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo
• If PR adds a configuration option, it has been added to the configuration file.

Additional Notes

Anything else we should know when reviewing?

[codecov-io]

Codecov Report

Merging #2949 into master will increase coverage by 0.56%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2949      +/-   ##
==========================================
+ Coverage   84.95%   85.51%   +0.56%     
==========================================
  Files         662        9     -653     
  Lines       37170      718   -36452     
  Branches     4396       94    -4302     
==========================================
- Hits        31577      614   -30963     
+ Misses       4307       73    -4234     
+ Partials     1286       31    -1255