Issue #6195: fix doctest to no longer try to read 'source' data from

binary files.

Lib/doctest.py

@@ -812,7 +812,17 @@ class DocTestFinder:
         # DocTestFinder._find_lineno to find the line number for a
         # given object's docstring.
         try:
-            file = inspect.getsourcefile(obj) or inspect.getfile(obj)
+            file = inspect.getsourcefile(obj)
+        except TypeError:
+            source_lines = None
+        else:
+            if not file:
+                # Check to see if it's one of our special internal "files"
+                # (see __patched_linecache_getlines).
+                file = inspect.getfile(obj)
+                if not file[0]+file[-2:] == '<]>': file = None
+            if file is None: source_lines = None
+            else:
                 if module is not None:
                     # Supply the module globals in case the module was
                     # originally loaded via a PEP 302 loader and
@@ -824,8 +834,6 @@ class DocTestFinder:
                     source_lines = linecache.getlines(file)
                 if not source_lines:
                     source_lines = None
-        except TypeError:
-            source_lines = None
 
         # Initialize globals, and merge in extraglobs.
         if globs is None:

Lib/test/test_doctest.py

@@ -2288,6 +2288,17 @@ using the optional keyword argument `encoding`:
     >>> doctest.master = None  # Reset master.
 """
 
+def test_testmod(): r"""
+Tests for the testmod function.  More might be useful, but for now we're just
+testing the case raised by Issue 6195, where trying to doctest a C module would
+fail with a UnicodeDecodeError because doctest tried to read the "source" lines
+out of the binary module.
+
+    >>> import unicodedata
+    >>> doctest.testmod(unicodedata)
+    TestResults(failed=0, attempted=0)
+"""
+
 ######################################################################
 ## Main
 ######################################################################

Misc/NEWS

@@ -24,6 +24,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #6195: fixed doctest to no longer try to read 'source' data from
+  binary files.
+
 - Issue #5262: Fixed bug in next rollover time computation in
   TimedRotatingFileHandler.