Print protoc error messages

[izumin5210]

WHY

WHAT

REF

[izumin5210]

[codecov-io]

Codecov Report

Merging #136 into master will increase coverage by 0.17%.
The diff coverage is 46.66%.

@@            Coverage Diff             @@
##           master     #136      +/-   ##
==========================================
+ Coverage   61.49%   61.67%   +0.17%     
==========================================
  Files          39       39              
  Lines        1322     1328       +6     
==========================================
+ Hits          813      819       +6     
  Misses        452      452              
  Partials       57       57

Impacted Files	Coverage Δ
pkg/protoc/wrapper.go	67.27% <0%> (ø)	⬆️
pkg/cli/nop_ui.go	0% <0%> (ø)	⬆️
pkg/cli/ui.go	90.9% <100%> (+0.9%)	⬆️

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