Add __all__ to graph package

skimage/graph/__init__.py

@@ -1,10 +1,7 @@
-try:
-    from .spath import shortest_path
-    from .mcp import MCP, MCP_Geometric, route_through_array
-except ImportError:
-    print """*** The cython extensions have not been compiled.  Run
+from .spath import shortest_path
+from .mcp import MCP, MCP_Geometric, route_through_array
 
-python setup.py build_ext -i
-
-in the source directory to build in-place.  Please refer to INSTALL.txt
-for further detail."""
+__all__ = ['shortest_path',
+           'MCP',
+           'MCP_Geometric',
+           'route_through_array']