Don't measure mock.py when we measure our coverage.

2 files changed, 2 insertions, 1 deletions

diff --git a/coverage/codeunit.py b/coverage/codeunit.py
index e3107052..6d156da7 100644
--- a/coverage/codeunit.py
+++ b/coverage/codeunit.py
@@ -34,6 +34,7 @@ def code_unit_factory(morfs, file_locator, omit_prefixes=None):
     code_units = [CodeUnit(morf, file_locator) for morf in morfs]
     
     if omit_prefixes:
+        assert not isinstance(omit_prefixes, string_class) # common mistake
         prefixes = [file_locator.abs_file(p) for p in omit_prefixes]
         filtered = []
         for cu in code_units:
diff --git a/test/coverage_coverage.py b/test/coverage_coverage.py
index 64380ab7..874cdd6f 100644
--- a/test/coverage_coverage.py
+++ b/test/coverage_coverage.py
@@ -46,4 +46,4 @@ cov.exclude("def __repr__")
 cov.exclude("if __name__ == .__main__.:")
 cov.exclude("raise AssertionError")
 
-cov.html_report(directory=HTML_DIR, ignore_errors=True)
+cov.html_report(directory=HTML_DIR, ignore_errors=True, omit_prefixes=["mock"])