fix: race condition on data file shouldn't break combining. #1522

1 files changed, 2 insertions, 0 deletions

diff --git a/coverage/data.py b/coverage/data.py
index 16fb9a8a..baddaddd 100644
--- a/coverage/data.py
+++ b/coverage/data.py
@@ -161,6 +161,8 @@ def combine_parallel_data(
                     # The CoverageException has the file name in it, so just
                     # use the message as the warning.
                     data._warn(str(exc))
+                if message:
+                    message(f"Couldn't combine data file {rel_file_name}: {exc}")
                 delete_this_one = False
             else:
                 data.update(new_data, aliases=aliases)