Add exception processing to properly report gerrit errors
Add exception processing to properly report gerrit errors

Catch chromite errors and terminate gracefully making it easier to
understand what exactly went wrong.

BUG=none
TEST=manual
  . tried running commands triggering errors, observed error messages:

$ gerrit review 38487 1
error: Change is closed
one or more approvals failed; review output above

Change-Id: I4d641f1c6f1dd37ef3fadb879cef286f03ec496d
Signed-off-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/56421
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite