feat: warnings are now real warnings

This makes coverage warnings visible when running test suites under
pytest.  But it also means some uninteresting warnings would show up in
our own test suite, so we had to catch or suppress those.

1 files changed, 5 insertions, 0 deletions

diff --git a/coverage/exceptions.py b/coverage/exceptions.py
index ed96fb21..6631e1ad 100644
--- a/coverage/exceptions.py
+++ b/coverage/exceptions.py
@@ -46,3 +46,8 @@ class StopEverything(BaseCoverageException):
 
     """
     pass
+
+
+class CoverageWarning(Warning):
+    """A warning from Coverage.py."""
+    pass