Use sys.exit(...) instead of exit(...): exit(...) should not be used in programs
Backport 3-of-6 for Core PR10781
Depends on D2150
Test Plan: N/A as these scripts are not used. This is a dependency for other backports.
Reviewers: deadalnix, schancel, #bitcoin_abc, Fabien
Reviewed By: schancel, #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D2151