デバッグメッセージの出力方法を変更

[shinya]

自動マージができなかった時のデバッグ出力で、JSONがエスケープできていなかったため、出力方法を変更。

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4fa87c1) 55.38% compared to head (fffa6d9) 55.38%.
Report is 7 commits behind head on master.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #838   +/-   ##
=======================================
  Coverage   55.38%   55.38%           
=======================================
  Files          75       75           
  Lines        8908     8908           
=======================================
  Hits         4934     4934           
  Misses       3974     3974           

Flag	Coverage Δ
tests	55.38% <ø> (ø)

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