Enable ruff DTZ rules and all datetime calls now use an explicit timezone

Author: tleonhardt

cmd2/cmd2.py

@@ -2562,7 +2562,7 @@ def onecmd_plus_hooks(
 
                     redir_saved_state = self._redirect_output(statement)
 
-                timestart = datetime.datetime.now()
+                timestart = datetime.datetime.now(tz=datetime.timezone.utc)
 
                 # precommand hooks
                 precmd_data = plugin.PrecommandData(statement)
@@ -2588,7 +2588,7 @@ def onecmd_plus_hooks(
                 stop = self.postcmd(stop, statement)
 
                 if self.timing:
-                    self.pfeedback(f'Elapsed: {datetime.datetime.now() - timestart}')
+                    self.pfeedback(f'Elapsed: {datetime.datetime.now(tz=datetime.timezone.utc) - timestart}')
             finally:
                 # Get sigint protection while we restore stuff
                 with self.sigint_protection:

pyproject.toml

@@ -169,9 +169,9 @@ select = [
     # "CPY", # flake8-copyright (warn about missing copyright notice at top of file - currently in preview)
     # "D",    # pydocstyle (warn about things like missing docstrings)
     # "DOC", # pydoclint (docstring warnings - currently in preview)
-    "DJ", # flake8-django (Django-specific warnings)
-    # "DTZ", # flake8-datetimez (warn about datetime calls where no timezone is specified)
-    "E", # pycodestyle errors (warn about major stylistic issues like mixing spaces and tabs)
+    "DJ",  # flake8-django (Django-specific warnings)
+    "DTZ", # flake8-datetimez (warn about datetime calls where no timezone is specified)
+    "E",   # pycodestyle errors (warn about major stylistic issues like mixing spaces and tabs)
     # "EM", # flake8-errmsg (warn about exceptions that use string literals that aren't assigned to a variable first)
     # "ERA",  # eradicate (warn about commented-out code)
     # "EXE", # flake8-executable (warn about files with a shebang present that aren't executable or vice versa)