run setup_dev_environment.py with python3

[speezepearson]

The file contains f-string syntax, but python on Macs still means (and perhaps will (and perhaps should) always mean) python2.7:

~ $ python --version
Python 2.7.18
~ $ cd src/client
~/s/client (master) $ ./tools/setup_dev_environment.py
  File "./tools/setup_dev_environment.py", line 48
    f"Requested invalid python versions: {invalid_versions}.\n"
                                                              ^
SyntaxError: invalid syntax

[codecov]

Codecov Report

Merging #3188 (52c384b) into master (e6445cd) will increase coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3188      +/-   ##
==========================================
+ Coverage   78.88%   79.03%   +0.14%     
==========================================
  Files         210      210              
  Lines       27636    27636              
==========================================
+ Hits        21802    21842      +40     
+ Misses       5834     5794      -40     

Flag	Coverage Δ
functest	57.15% <ø> (+0.03%)	⬆️
unittest	68.88% <ø> (+0.13%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
wandb/filesync/step_prepare.py	92.85% <0.00%> (-1.43%)	⬇️
wandb/sdk/launch/docker.py	86.33% <0.00%> (-1.10%)	⬇️
wandb/sdk/wandb_settings.py	94.30% <0.00%> (-0.80%)	⬇️
wandb/sdk/internal/stats.py	67.22% <0.00%> (-0.56%)	⬇️
wandb/sdk/lib/redirect.py	86.53% <0.00%> (-0.18%)	⬇️
wandb/sdk/lib/git.py	76.35% <0.00%> (ø)
wandb/sdk/wandb_run.py	87.87% <0.00%> (+0.26%)	⬆️
wandb/sdk/internal/sender.py	91.71% <0.00%> (+0.27%)	⬆️
wandb/sdk/internal/internal_api.py	83.61% <0.00%> (+0.56%)	⬆️
wandb/apis/internal.py	92.52% <0.00%> (+0.93%)	⬆️
... and 4 more

[dmitryduev]

🙌🏻