Cleanup recent generalization in post mortem debugger

Remove unnecessary default arguments and constants in
the post mortem debugger code.

Also remove exception internationalization in testing code.

Change-Id: I66ba3248a7ff502fa92e1c46f40e280c503524a2
tox.ini: Prevent casual addition of bash dependency

While bash is not available on every environments, there seems to be
a tendency to introduce more bash dependency very casually.  This check
is intended to be a reminder to give people a chance to consider
alternatives.

Related-Bug: #1398266
Change-Id: I5103e0d7c111880d9a02dd93de56c567066ed14c
Merge "Cleanup recent generalization in post mortem debugger"
Merge "tox.ini: Prevent casual addition of bash dependency"