Added function xml.sax.saxutils.quoteattr().

This closes SF bug #440351.  It should not be moved to Python 2.1.1.
diff --git a/Lib/test/output/test_sax b/Lib/test/output/test_sax
index de49c80..b14cf94 100644
--- a/Lib/test/output/test_sax
+++ b/Lib/test/output/test_sax
@@ -1,6 +1,7 @@
 test_sax
 Passed test_attrs_empty
 Passed test_attrs_wattr
+Passed test_double_quoteattr
 Passed test_escape_all
 Passed test_escape_basic
 Passed test_escape_extra
@@ -25,10 +26,13 @@
 Passed test_make_parser2
 Passed test_nsattrs_empty
 Passed test_nsattrs_wattr
+Passed test_quoteattr_basic
+Passed test_single_double_quoteattr
+Passed test_single_quoteattr
 Passed test_xmlgen_basic
 Passed test_xmlgen_content
 Passed test_xmlgen_content_escape
 Passed test_xmlgen_ignorable
 Passed test_xmlgen_ns
 Passed test_xmlgen_pi
-32 tests, 0 failures
+36 tests, 0 failures
diff --git a/Lib/test/test_sax.py b/Lib/test/test_sax.py
index f4b43fe..62705c9 100644
--- a/Lib/test/test_sax.py
+++ b/Lib/test/test_sax.py
@@ -8,7 +8,7 @@
 except SAXReaderNotAvailable:
     # don't try to test this module if we cannot create a parser
     raise ImportError("no XML parsers available")
-from xml.sax.saxutils import XMLGenerator, escape, XMLFilterBase
+from xml.sax.saxutils import XMLGenerator, escape, quoteattr, XMLFilterBase
 from xml.sax.expatreader import create_parser
 from xml.sax.xmlreader import InputSource, AttributesImpl, AttributesNSImpl
 from cStringIO import StringIO
@@ -69,6 +69,25 @@
 def test_escape_extra():
     return escape("Hei på deg", {"å" : "å"}) == "Hei på deg"
 
+# ===== quoteattr
+
+def test_quoteattr_basic():
+    return quoteattr("Donald Duck & Co") == '"Donald Duck & Co"'
+
+def test_single_quoteattr():
+    return (quoteattr('Includes "double" quotes')
+            == '\'Includes "double" quotes\'')
+
+def test_double_quoteattr():
+    return (quoteattr("Includes 'single' quotes")
+            == "\"Includes 'single' quotes\"")
+
+def test_single_double_quoteattr():
+    return (quoteattr("Includes 'single' and \"double\" quotes")
+            == "\"Includes 'single' and "double" quotes\"")
+
+# ===== make_parser
+
 def test_make_parser():
     try:
         # Creating a parser should succeed - it should fall back
diff --git a/Lib/xml/sax/saxutils.py b/Lib/xml/sax/saxutils.py
index e592f2a..bf1f5f3 100644
--- a/Lib/xml/sax/saxutils.py
+++ b/Lib/xml/sax/saxutils.py
@@ -27,6 +27,27 @@
         data = data.replace(chars, entity)
     return data
 
+def quoteattr(data, entities={}):
+    """Escape and quote an attribute value.
+
+    Escape &, <, and > in a string of data, then quote it for use as
+    an attribute value.  The \" character will be escaped as well, if
+    necessary.
+
+    You can escape other strings of data by passing a dictionary as
+    the optional entities parameter.  The keys and values must all be
+    strings; each key will be replaced with its corresponding value.
+    """
+    data = escape(data, entities)
+    if '"' in data:
+        if "'" in data:
+            data = '"%s"' % data.replace('"', "&quot;")
+        else:
+            data = "'%s'" % data
+    else:
+        data = '"%s"' % data
+    return data
+
 
 class XMLGenerator(handler.ContentHandler):