hotfix: v0.5.1 fix iss#23

Document.add_picture() raises ValueError when document contains VML
drawing

HISTORY.rst

@@ -3,6 +3,13 @@
 Release History
 ---------------
 
+0.5.1 (2014-04-02)
+++++++++++++++++++
+
+- Fix issue #23, `Document.add_picture()` raises ValueError when document
+  contains VML drawing.
+
+
 0.5.0 (2014-03-02)
 ++++++++++++++++++
 

docx/__init__.py

@@ -2,7 +2,7 @@
 
 from docx.api import Document  # noqa
 
-__version__ = '0.5.0'
+__version__ = '0.5.1'
 
 
 # register custom Part classes with opc package reader

docx/parts/document.py

@@ -87,7 +87,7 @@ def next_id(self):
         document, without regard to the element type it appears on.
         """
         id_str_lst = self._element.xpath('//@id')
-        used_ids = [int(id_str) for id_str in id_str_lst]
+        used_ids = [int(id_str) for id_str in id_str_lst if id_str.isdigit()]
         for n in range(1, len(used_ids)+2):
             if n not in used_ids:
                 return n

tests/parts/test_document.py

@@ -244,7 +244,7 @@ def inline_shapes_fixture(self, request, InlineShapes_):
 
     @pytest.fixture(params=[
         ((), 1), ((1,), 2), ((2,), 1), ((1, 2, 3), 4), ((1, 2, 4), 3),
-        ((0, 0), 1), ((0, 0, 1, 3), 2),
+        ((0, 0), 1), ((0, 0, 1, 3), 2), (('foo', 1, 2), 3), ((1, 'bar'), 2)
     ])
     def next_id_fixture(self, request):
         existing_ids, expected_id = request.param