More typo fixes

theano/gof/fg.py

@@ -86,7 +86,7 @@ class FunctionGraph(utils.object2):
         is added via the constructor.  How constructed is the FunctionGraph?
 
         :param clone: If true, we will clone the graph. This is
-        usefull to remove the constant cache problem.
+        useful to remove the constant cache problem.
 
         """
         if clone:
@@ -138,8 +138,8 @@ class FunctionGraph(utils.object2):
         if getattr(r, 'cached', False):
             raise CachedConstantError(
                 "You manually constructed a FunctionGraph, but you passed it a"
-                " graph that have cached constant. This should happen."
-                " Clone the graph before building the FunctionGraph")
+                " graph that has a cached constant. This should not happen."
+                " Clone the graph before building the FunctionGraph.")
         if (hasattr(r, 'fgraph') and
             r.fgraph is not None and
             r.fgraph is not self):

theano/tensor/utils.py

@@ -89,8 +89,8 @@ def shape_of_variables(fgraph, input_shapes):
     if any([i not in fgraph.inputs for i in input_shapes.keys()]):
         raise ValueError(
             "input_shapes keys aren't in the fgraph.inputs. FunctionGraph()"
-            " interface changed. Now by default, it clone the graph it receive."
-            " To have the old behavior, give him this new parameter `clone=False`.")
+            " interface changed. Now by default, it clones the graph it receives."
+            " To have the old behavior, give it this new parameter `clone=False`.")
 
     numeric_input_dims  = [dim for inp in fgraph.inputs
                                for dim in input_shapes[inp]]