Fixed non-bool return value.

geoarray/baseclasses.py

@@ -369,7 +369,7 @@ class GeoArray(object):
     def is_rotated(self):
         # type: () -> bool
         """Return 'True' if the image has a rotation in the map info (i.e., is pseudo-projected)."""
-        return self.gt[2] or self.gt[4]
+        return self.gt[2] != 0 or self.gt[4] != 0
 
     @property
     def nodata(self):