util: Port util to python3

This commit is the result of running 2to3 converter on the util
subdirectory

JIRA: https://gem5.atlassian.net/browse/GEM5-832

Change-Id: I4e7e2d2b1b99f7bcc5fe0f6dc5d25880323616eb
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/37797
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

util/git-commit-msg.py

@@ -46,7 +46,7 @@ def _printErrorQuit(error_message):
     print(error_message)
 
     print("The commit has been cancelled, but a copy of it can be found in "
-            + sys.argv[1] + " : ")
+          + sys.argv[1] + " : ")
 
     print("""
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