add "some warnings detected" to ParseError printing when all problems are warnings

[ericphanson]

I totally missed that the (..) issue from #350 was a warning rather than an error; I think probably bc the bold red part says ERROR: ParseError: and then the very light part says "Warning". Here I propose add to text to make it clearer by emphasizing warning vs error on the first line.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.17%. Comparing base (a6f2d15) to head (4069462).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #423      +/-   ##
==========================================
+ Coverage   94.61%   96.17%   +1.56%     
==========================================
  Files          14       14              
  Lines        4178     4187       +9     
==========================================
+ Hits         3953     4027      +74     
+ Misses        225      160      -65     

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[c42f]

Do we need this for errors? It seems kind of redundant in that case.

Perhaps we just add the extra text when the error is due only to parser warnings?

[c42f]

@ericphanson I invited you as a collaborator on this repo (if you like) feel free to merge this when you're ready :)