#2501 xml.sax.parser doesn't terminate when given a filename; enable some more tests!

Reviewed by myself
diff --git a/Lib/xml/sax/xmlreader.py b/Lib/xml/sax/xmlreader.py
index 6264ee3..5ce30b0 100644
--- a/Lib/xml/sax/xmlreader.py
+++ b/Lib/xml/sax/xmlreader.py
@@ -119,7 +119,7 @@
         self.prepareParser(source)
         file = source.getByteStream()
         buffer = file.read(self._bufsize)
-        while buffer != "":
+        while buffer:
             self.feed(buffer)
             buffer = file.read(self._bufsize)
         self.close()