test: exclude statement from coverage report

In the move to Python 3.9, we are subject to a coverage behavior that
has yet to be corrected.
In the interest of keeping the coverage report to 100%, we exclude
the statement that coverage.py reports as not being executed, despite
it being executed via tests.

Refs: nedbat/coveragepy#1041

Signed-off-by: Mike Fiedler <[email protected]>

warehouse/search/tasks.py

@@ -196,7 +196,7 @@ def reindex(self, request):
                 raise
             finally:
                 request.db.rollback()
-                request.db.close()
+                request.db.close()  # pragma: no cover
 
             # Now that we've finished indexing all of our data we can update the
             # replicas and refresh intervals.