Enable verbose logging with --debug

This helps ensure that all relevant context is presented when a failure
happens and diagnosis is being done through the use of `--debug`.

Author: pradyunsg

src/pip/_internal/cli/base_command.py

@@ -172,6 +172,8 @@ def _main(self, args: List[str]) -> int:
 
         # Set verbosity so that it can be used elsewhere.
         self.verbosity = options.verbose - options.quiet
+        if options.debug_mode:
+            self.verbosity = 2
 
         reconfigure(no_color=options.no_color)
         level_number = setup_logging(