logging: Abbreviate log-level names to 4 characters.

These are long enough to still be self-explanatory (the only one I'm
at all in doubt about there is DEBG; I avoided "DBUG" because it reads
"BUG" which suggests a high-priority message, and those are the
opposite of that), while saving a good bit of horizontal space
vs. padding everything to the 8 characters of "CRITICAL".

Also add a linter exception to allow easy-to-read alignment here,
similar to several existing exceptions for other alignment cases.

tools/linter_lib/pep8.py

@@ -40,6 +40,11 @@ def check_pep8(files):
         # these may make the code less readable.
         'E226',
 
+        # "multiple spaces after ':'"
+        # This is the `{}` analogue of E221, and these are similarly being used
+        # for alignment.
+        'E241',
+
         # "unexpected spaces around keyword / parameter equals"
         # Many of these should be fixed, but many are also being used for
         # alignment/making the code easier to read.