pySim.log: apply cmd2 colors through _style()

The color scheme takes either
- a raw escape sequence like "\033[33m" (pySim-read,
pySim-prog, contrib/csv-to-pgsql.py)
- a cmd2 color object (pySim-shell)

Color of cmd2 >= 3.0.0 is a StrEnum, which led to
pySim-shell warnings like

  yellowWARNING: EF.DIR seems to be empty!

with a stray reset at the end.

Fixed by exclusing Enum from the raw sequence branch.

Change-Id: I8bae9fc3c54f1dab481d743d3b68e32e9d09267a

pySim/log.py

@@ -24,6 +24,7 @@
 #
 
 import logging
+import enum
 import cmd2
 from packaging import version
 
@@ -126,7 +127,7 @@ class PySimLogger:
                 formatted_message = logging.Formatter.format(PySimLogger.__formatter, record)
             color = PySimLogger.colors.get(record.levelno)
             if color:
-                if isinstance(color, str):
+                if isinstance(color, str) and not isinstance(color, enum.Enum):
                     PySimLogger.print_callback(color + formatted_message + "\033[0m")
                 else:
                     PySimLogger.print_callback(_style(formatted_message, fg = color))