Limit the number of testing (~x86) packages.
I'm not quite sure why wxpython 2.9 is being drawn in, but disabling
these use flags seems to fix it.
# required by dev-python/matplotlib (argument)
dev-python/matplotlib ~x86
-
-# required by dev-python/matplotlib-1.2.0-r2[wxwidgets],
-# required by dev-python/ipython-0.13.1-r1[matplotlib],
-# required by dev-python/sympy-0.7.2[ipython],
-# required by dev-python/sympy (argument)
-dev-python/wxpython ~x86
--- /dev/null
+# don't drag in a testing version of wxpython and wxGTK
+dev-python/ipython -wxwidgets
+dev-python/matplotlib -wxwidgets