Remove catch + sys.exit idiom

This is bad, python already prints exceptino message and exit with
non-zero code when an exception is raised, no need to catch the
exception just to print it. In addition, printing an exception does not
print stacktrace, so catch + sys.exit provide less information than
python's default behavior.

Test: th
Change-Id: If6cf2e34d4ebc9f7d172063b4396bf4377dad447

tools/releasetools/check_partition_sizes.py

@@ -300,8 +300,5 @@ if __name__ == "__main__":
   try:
     common.CloseInheritedPipes()
     main(sys.argv[1:])
-  except common.ExternalError:
-    logger.exception("\n   ERROR:\n")
-    sys.exit(1)
   finally:
     common.Cleanup()