python: Use universal_newlines to get str from subprocess.

We can replace ‘universal_newlines’ with ‘text’ when we bump our
minimum Python version to 3.7.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/logging_handlers.py

@@ -25,7 +25,8 @@ def try_git_describe() -> Optional[str]:
             ['git', 'describe', '--tags', '--match=[0-9]*', '--always', '--dirty', '--long'],
             stderr=subprocess.PIPE,
             cwd=os.path.join(os.path.dirname(__file__), '..'),
-        ).strip().decode('utf-8')
+            universal_newlines=True,
+        ).strip()
     except (FileNotFoundError, subprocess.CalledProcessError):  # nocoverage
         return None