python: Apply Black formatter to Python files

The command executed was `black src configs tests util`.

Change-Id: I8dfaa6ab04658fea37618127d6ac19270028d771
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47024
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/m5/__init__.py

@@ -46,7 +46,8 @@ if in_gem5:
     from . import objects
     from . import params
     from . import stats
-    if defines.buildEnv['USE_SYSTEMC']:
+
+    if defines.buildEnv["USE_SYSTEMC"]:
         from . import systemc
         from . import tlm
     from . import util
@@ -54,4 +55,3 @@ if in_gem5:
     from .event import *
     from .main import main
     from .simulate import *
-