pw_presubmit: Add logging to pragma_once check

This makes it easier to track down specific files if exceptions occur.

Change-Id: Iacba4aa6676ea7457c7748701eedc322b2c9144b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/113515
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Reviewed-by: Alexei Frolov <frolv@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>

pw_presubmit/py/pw_presubmit/cpp_checks.py

@@ -13,6 +13,8 @@
 # the License.
 """C++-related checks."""
 
+import logging
+
 from pw_presubmit import (
  build,
  Check,
@@ -21,12 +23,15 @@
  filter_paths,
 )
 
+_LOG: logging.Logger = logging.getLogger(__name__)
+
 
 @filter_paths(endswith=format_code.CPP_HEADER_EXTS, exclude=(r'\.pb\.h$', ))
 def pragma_once(ctx: PresubmitContext) -> None:
  """Presubmit check that ensures all header files contain '#pragma once'."""
 
  for path in ctx.paths:
+ _LOG.debug('Checking %s', path)
  with open(path) as file:
  for line in file:
  if line.startswith('#pragma once'):