Merge pull request matplotlib#1967 from mdboom/svg-comment-escape

svg double hyphen in plot title --

Author: mdboom

lib/matplotlib/backends/backend_svg.py

@@ -1,6 +1,6 @@
 from __future__ import division
 
-import os, base64, tempfile, urllib, gzip, io, sys, codecs
+import os, base64, tempfile, urllib, gzip, io, sys, codecs, re
 
 import numpy as np
 
@@ -71,6 +71,11 @@ def escape_cdata(s):
     s = s.replace(u">", u">")
     return s
 
+_escape_xml_comment = re.compile(r'-(?=-)')
+def escape_comment(s):
+    s = escape_cdata(s)
+    return _escape_xml_comment.sub('- ', s)
+
 def escape_attrib(s):
     s = s.replace(u"&", u"&")
     s = s.replace(u"'", u"'")
@@ -146,7 +151,7 @@ def start(self, tag, attrib={}, **extra):
     def comment(self, comment):
         self.__flush()
         self.__write(self.__indentation[:len(self.__tags)])
-        self.__write(u"<!-- %s -->\n" % escape_cdata(comment))
+        self.__write(u"<!-- %s -->\n" % escape_comment(comment))
 
     ##
     # Adds character data to the output stream.