Protect ourselves from mock'ed os. #416

1 files changed, 6 insertions, 2 deletions

diff --git a/coverage/collector.py b/coverage/collector.py
index 42a97f1a..0a43d87c 100644
--- a/coverage/collector.py
+++ b/coverage/collector.py
@@ -3,14 +3,18 @@
 
 """Raw data collector for coverage.py."""
 
-import os, sys
+import os
+import sys
 
 from coverage import env
 from coverage.backward import iitems
 from coverage.files import abs_file
-from coverage.misc import CoverageException
+from coverage.misc import CoverageException, isolate_module
 from coverage.pytracer import PyTracer
 
+os = isolate_module(os)
+
+
 try:
     # Use the C extension code when we can, for speed.
     from coverage.tracer import CTracer, CFileDisposition   # pylint: disable=no-name-in-module