python: be more robust to different graphviz version in tests

* wrap/python/tests/ipnbdoctest.py: Ignore anything that look like an
SVG coordinate to compare outputs.

wrap/python/tests/ipnbdoctest.py

@@ -67,6 +67,13 @@ def sanitize(s):
     # normalize UUIDs:
     s = re.sub(r'[a-f0-9]{8}(\-[a-f0-9]{4}){3}\-[a-f0-9]{12}', 'U-U-I-D', s)
 
+    # SVG generated by graphviz may put note at different positions
+    # depending on the graphviz build.  Let's just strip anything that
+    # look like a position.
+    s = re.sub(r'<path d="[^"]*"', '<path', s)
+    s = re.sub(r'x="[0-9.]+"', 'x=""', s)
+    s = re.sub(r'y="[0-9.]+"', 'y=""', s)
+
     return s