Add some warnings about environment variables when running commands

[JamesWrigley]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 63.64%. Comparing base (d730a68) to head (97e0f8e).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/channel.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #23   +/-   ##
=======================================
  Coverage   63.64%   63.64%           
=======================================
  Files          11       11           
  Lines        3012     3012           
=======================================
  Hits         1917     1917           
  Misses       1095     1095           

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