Handle case where git is not installed

[cb22]

No description provided.

[codecov]

Codecov Report

Merging #398 (00d4633) into master (fac16b6) will decrease coverage by 0.09%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #398      +/-   ##
==========================================
- Coverage   86.14%   86.05%   -0.10%     
==========================================
  Files          14       14              
  Lines        1711     1714       +3     
==========================================
+ Hits         1474     1475       +1     
- Misses        237      239       +2     

Impacted Files	Coverage Δ
safety/util.py	81.37% <50.00%> (-0.36%)	⬇️

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