1 files changed, 23 insertions, 3 deletions
diff --git a/coverage/codeunit.py b/coverage/codeunit.py
index ac90cb2..2b581d0 100644
--- a/coverage/codeunit.py
+++ b/coverage/codeunit.py
@@ -2,7 +2,7 @@
 
 import glob, os
 
-from coverage.backward import string_class, StringIO
+from coverage.backward import open_source, string_class, StringIO
 from coverage.misc import CoverageException
 
 
@@ -52,7 +52,7 @@ class CodeUnit(object):
         else:
             f = morf
         # .pyc files should always refer to a .py instead.
-        if f.endswith('.pyc'):
+        if f.endswith('.pyc') or f.endswith('.pyo'):
             f = f[:-1]
         elif f.endswith('$py.class'): # jython
             f = f[:-9] + ".py"
@@ -106,7 +106,7 @@ class CodeUnit(object):
         """Return an open file for reading the source of the code unit."""
         if os.path.exists(self.filename):
             # A regular text file: open it.
-            return open(self.filename)
+            return open_source(self.filename)
 
         # Maybe it's in a zip file?
         source = self.file_locator.get_zip_data(self.filename)
@@ -117,3 +117,23 @@ class CodeUnit(object):
         raise CoverageException(
             "No source for code %r." % self.filename
             )
+
+    def should_be_python(self):
+        """Does it seem like this file should contain Python?
+
+        This is used to decide if a file reported as part of the exection of
+        a program was really likely to have contained Python in the first
+        place.
+
+        """
+        # Get the file extension.
+        _, ext = os.path.splitext(self.filename)
+
+        # Anything named *.py* should be Python.
+        if ext.startswith('.py'):
+            return True
+        # A file with no extension should be Python.
+        if not ext:
+            return True
+        # Everything else is probably not Python.
+        return False