Python: improve messaging

Author: yoff

python/extractor/semmle/cmdline.py

@@ -228,15 +228,17 @@ def parse(command_line):
 
     if 'CODEQL_EXTRACTOR_PYTHON_DONT_EXTRACT_STDLIB' in os.environ:
         options.extract_stdlib = False
-        print ("Warning: CODEQL_EXTRACTOR_PYTHON_DONT_EXTRACT_STDLIB is deprecated; the default is now to not extract the standard library.")
+        print ("WARNING: CODEQL_EXTRACTOR_PYTHON_DONT_EXTRACT_STDLIB is deprecated; the default is now to not extract the standard library.")
 
     if 'CODEQL_EXTRACTOR_PYTHON_EXTRACT_STDLIB' in os.environ:
         options.extract_stdlib = True
 
     options.prune = True
 
     if options.extract_stdlib:
-        print ("Warning: The analysis will extract the standard library. This behavior is deprecated and will be removed in a future release. We expect it to be gone in CLI version 2.20.0.")
+        print ("WARNING: The analysis will extract the standard library. This behavior is deprecated and will be removed in a future release. We expect it to be gone in CLI version 2.20.0.")
+    else:
+        print ("INFO: The Python extractor has recently stopped extracting the standard library by default. If you encounter problems, please let us know by submitting an issue to https://github.com/github/codeql. It is possible to re-enable extraction of the standard library by setting the environment variable CODEQL_EXTRACTOR_PYTHON_EXTRACT_STDLIB.")
 
     return options, args