exclude Versioneer source file from coverage measurement/reporting

.coveragerc

@@ -6,6 +6,18 @@ source =
 branch = True
 parallel = True
 
+omit =
+    # The Versioneer version file in the repository is generated by
+    # Versioneer.  Let's call it Versioneer's responsibility to ensure it
+    # works and not pay attention to our test suite's coverage of it.  Also,
+    # the way Versioneer works is that the source file in the repository is
+    # different from the source file in an installation - which is where we
+    # measure coverage.  When the source files differ like this, it's very
+    # difficult to produce a coherent coverage report (measurements against
+    # one source file are meaningless when looking at a different source
+    # file).
+    src/_zkapauthorizer/_version.py
+
 [paths]
 source =
     src/