Issue #4050: inspect.findsource/getsource now raise an IOError if the 'source'
file is a binary.  Patch by Brodie Rao, test by Daniel Diniz.
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 1453f3b..3305c8d 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -523,7 +523,9 @@
     or code object.  The source code is returned as a list of all the lines
     in the file and the line number indexes a line in that list.  An IOError
     is raised if the source code cannot be retrieved."""
-    file = getsourcefile(object) or getfile(object)
+    file = getsourcefile(object)
+    if not file:
+        raise IOError('source code not available')
     module = getmodule(object, file)
     if module:
         lines = linecache.getlines(file, module.__dict__)