More verbose 'fail' msgs. Don't rely on executed tools err msg (#737)
More verbose 'fail' msgs. Don't rely on executed tools err msg (#737)

* More verbose 'fail' msgs. Don't rely on executed tools err msg

* run buildifier

Co-authored-by: Matt Mackay <4455148c4d3781bbffad60d717d76cf96a48724f@gmail.com>
bazelbuild/rules_python,bazelbuild/rules_python,bazelbuild/rules_python