Improve the config missing message when running emulator

[chasefleming]

Closes #1789

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For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

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

Project coverage is 28.47%. Comparing base (888f6d2) to head (278fc15).

Files with missing lines	Patch %	Lines
internal/emulator/start.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1835   +/-   ##
=======================================
  Coverage   28.47%   28.47%           
=======================================
  Files          95       95           
  Lines        6490     6490           
=======================================
  Hits         1848     1848           
  Misses       4462     4462           
  Partials      180      180           

Flag	Coverage Δ
unittests	28.47% <0.00%> (ø)

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