BF: Builder failing to sync new git projects

[peircej]

The switch to use check_output meant that when there was no
existing git repo in the folder the call git branch --show-current
returns non-zero but with check_output that causes an error to be
raised. We don't want that - we want to know it happened and move on.

[codecov]

Codecov Report

Merging #3626 (33b3d80) into release (485d29c) will increase coverage by 0.03%.
The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           release    #3626      +/-   ##
===========================================
+ Coverage    43.13%   43.16%   +0.03%     
===========================================
  Files          267      267              
  Lines        52629    52691      +62     
  Branches      9063     9082      +19     
===========================================
+ Hits         22700    22743      +43     
- Misses       27616    27624       +8     
- Partials      2313     2324      +11     

Impacted Files	Coverage Δ
psychopy/projects/pavlovia.py	22.13% <66.66%> (+1.68%)	⬆️
psychopy/app/builder/dialogs/paramCtrls.py	58.76% <0.00%> (-0.67%)	⬇️
psychopy/app/builder/builder.py	47.14% <0.00%> (-0.25%)	⬇️
psychopy/app/builder/dialogs/__init__.py	40.96% <0.00%> (-0.07%)	⬇️
psychopy/visual/basevisual.py	67.79% <0.00%> (-0.01%)	⬇️
psychopy/visual/line.py	91.42% <0.00%> (ø)
psychopy/colors.py	56.17% <0.00%> (+0.25%)	⬆️
psychopy/visual/form.py	64.15% <0.00%> (+0.34%)	⬆️
psychopy/visual/slider.py	69.50% <0.00%> (+0.50%)	⬆️
psychopy/tools/colorspacetools.py	75.58% <0.00%> (+1.05%)	⬆️
... and 1 more

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[coveralls]

Coverage increased (+0.03%) to 47.025% when pulling 33b3d80 on peircej:hotfix-git-check-branch into ceb51c1 on psychopy:release.