fix output writing in Py2 where io.StringIO does not support writing 'str'

Cython/Compiler/Annotate.py

@@ -11,7 +11,10 @@ from datetime import datetime
 from functools import partial
 from collections import defaultdict
 from xml.sax.saxutils import escape as html_escape
-from io import StringIO
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO  # does not support writing 'str' in Py2
 
 from . import Version
 from .Code import CCodeWriter

Cython/StringIOTree.py

-from io import StringIO
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO  # does not support writing 'str' in Py2
 
 
 class StringIOTree(object):