2to3: Apply nonzero fixer.

In Python 3 the `__nonzero__` class method is replaced by `__bool__`.
This only affects the MaskedArray class in numpy/oldnumeric/ma.py file
and the simplest solution is to provide both methods. I have my doubts
that the fixed up Python 3 version was correct or even tested, but I
think the current solution should work for as long as oldnumeric stays
in numpy.

Closes numpy#3073.

numpy/oldnumeric/ma.py

@@ -865,6 +865,18 @@ def __nonzero__(self):
         return bool(m is not nomask and m.any()
                     or d is not nomask and d.any())
 
+    def __bool__(self):
+        """returns true if any element is non-zero or masked
+
+        """
+        # XXX: This changes bool conversion logic from MA.
+        # XXX: In MA bool(a) == len(a) != 0, but in numpy
+        # XXX: scalars do not have len
+        m = self._mask
+        d = self._data
+        return bool(m is not nomask and m.any()
+                    or d is not nomask and d.any())
+
     def __len__ (self):
         """Return length of first dimension. This is weird but Python's
          slicing behavior depends on it."""
@@ -2134,10 +2146,13 @@ def asarray(data, dtype=None):
 # XXX: I is better to to change the masked_*_operation adaptors
 # XXX: to wrap ndarray methods directly to create ma.array methods.
 from types import MethodType
+
 def _m(f):
     return MethodType(f, None, array)
+
 def not_implemented(*args, **kwds):
     raise NotImplementedError("not yet implemented for numpy.ma arrays")
+
 array.all = _m(alltrue)
 array.any = _m(sometrue)
 array.argmax = _m(argmax)

tools/py3tool.py

@@ -73,7 +73,7 @@
     'methodattrs',
     'ne',
 #    'next',
-#    'nonzero',
+    'nonzero',
     'numliterals',
     'operator',
     'paren',