contrib: Use text=True in subprocess over manual encoding handling

All touched Python scripts already assume and require UTF8, so manually
specifying encoding or decoding for functions in the subprocess module
is redundant to just using text=True, which exists since Python 3.7

contrib/verify-commits/verify-commits.py

@@ -140,8 +140,8 @@ def main():
 
         # Check that the commit (and parents) was signed with a trusted key
         valid_sig = False
-        verify_res = subprocess.run([GIT, '-c', 'gpg.program={}/gpg.sh'.format(dirname), 'verify-commit', "--raw", current_commit], capture_output=True)
-        for line in verify_res.stderr.decode().splitlines():
+        verify_res = subprocess.run([GIT, '-c', 'gpg.program={}/gpg.sh'.format(dirname), 'verify-commit', "--raw", current_commit], text=True, capture_output=True)
+        for line in verify_res.stderr.splitlines():
             if line.startswith("[GNUPG:] VALIDSIG "):
                 key = line.split(" ")[-1]
                 valid_sig = key in trusted_keys
@@ -152,7 +152,7 @@ def main():
             if prev_commit != "":
                 print("No parent of {} was signed with a trusted key!".format(prev_commit), file=sys.stderr)
                 print("Parents are:", file=sys.stderr)
-                parents = subprocess.check_output([GIT, 'show', '-s', '--format=format:%P', prev_commit]).decode('utf8').splitlines()[0].split(' ')
+                parents = subprocess.check_output([GIT, 'show', '-s', '--format=format:%P', prev_commit], text=True).splitlines()[0].split(' ')
                 for parent in parents:
                     subprocess.call([GIT, 'show', '-s', parent], stdout=sys.stderr)
             else:
@@ -162,29 +162,29 @@ def main():
         # Check the Tree-SHA512
         if (verify_tree or prev_commit == "") and current_commit not in incorrect_sha512_allowed:
             tree_hash = tree_sha512sum(current_commit)
-            if ("Tree-SHA512: {}".format(tree_hash)) not in subprocess.check_output([GIT, 'show', '-s', '--format=format:%B', current_commit]).decode('utf8').splitlines():
+            if ("Tree-SHA512: {}".format(tree_hash)) not in subprocess.check_output([GIT, 'show', '-s', '--format=format:%B', current_commit], text=True).splitlines():
                 print("Tree-SHA512 did not match for commit " + current_commit, file=sys.stderr)
                 sys.exit(1)
 
         # Merge commits should only have two parents
-        parents = subprocess.check_output([GIT, 'show', '-s', '--format=format:%P', current_commit]).decode('utf8').splitlines()[0].split(' ')
+        parents = subprocess.check_output([GIT, 'show', '-s', '--format=format:%P', current_commit], text=True).splitlines()[0].split(' ')
         if len(parents) > 2:
             print("Commit {} is an octopus merge".format(current_commit), file=sys.stderr)
             sys.exit(1)
 
         # Check that the merge commit is clean
-        commit_time = int(subprocess.check_output([GIT, 'show', '-s', '--format=format:%ct', current_commit]).decode('utf8').splitlines()[0])
+        commit_time = int(subprocess.check_output([GIT, 'show', '-s', '--format=format:%ct', current_commit], text=True).splitlines()[0])
         check_merge = commit_time > time.time() - args.clean_merge * 24 * 60 * 60  # Only check commits in clean_merge days
         allow_unclean = current_commit in unclean_merge_allowed
         if len(parents) == 2 and check_merge and not allow_unclean:
-            current_tree = subprocess.check_output([GIT, 'show', '--format=%T', current_commit]).decode('utf8').splitlines()[0]
+            current_tree = subprocess.check_output([GIT, 'show', '--format=%T', current_commit], text=True).splitlines()[0]
 
             # This merge-tree functionality requires git >= 2.38. The
             # --write-tree option was added in order to opt-in to the new
             # behavior. Older versions of git will not recognize the option and
             # will instead exit with code 128.
             try:
-                recreated_tree = subprocess.check_output([GIT, "merge-tree", "--write-tree", parents[0], parents[1]]).decode('utf8').splitlines()[0]
+                recreated_tree = subprocess.check_output([GIT, "merge-tree", "--write-tree", parents[0], parents[1]], text=True).splitlines()[0]
             except subprocess.CalledProcessError as e:
                 if e.returncode == 128:
                     print("git v2.38+ is required for this functionality.", file=sys.stderr)