Fix python3 error

Author: isuruf

symengine/lib/symengine_wrapper.pyx

@@ -3088,19 +3088,10 @@ cdef class DenseMatrixBase(MatrixBase):
             return NotImplemented
 
     def __div__(a, b):
-        a = _sympify(a, False)
-        b = _sympify(b, False)
-        if isinstance(a, MatrixBase):
-            if isinstance(b, MatrixBase):
-                return a.mul_matrix(b.inv())
-            elif isinstance(b, Basic):
-                return a.mul_scalar(1/b)
-            else:
-                return NotImplemented
-        else:
-            return NotImplemented
+        return div_matrices(a, b)
 
-    __truediv__ = __div__
+    def __truediv__(a, b):
+        return div_matrices(a, b)
 
     def __sub__(a, b):
         a = _sympify(a, False)
@@ -3571,6 +3562,20 @@ cdef class DenseMatrixBase(MatrixBase):
     def expand(self, *args, **kwargs):
         return self.applyfunc(lambda x : x.expand())
 
+
+def div_matrices(a, b):
+    a = _sympify(a, False)
+    b = _sympify(b, False)
+    if isinstance(a, MatrixBase):
+        if isinstance(b, MatrixBase):
+            return a.mul_matrix(b.inv())
+        elif isinstance(b, Basic):
+            return a.mul_scalar(1/b)
+        else:
+            return NotImplemented
+    else:
+        return NotImplemented
+
 class DenseMatrixBaseIter(object):
 
     def __init__(self, d):