replace remaining basestring by six.string_types

src/sage/quivers/algebra.py

@@ -18,6 +18,7 @@
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 
+import six
 from sage.misc.cachefunc import cached_method
 from sage.combinat.free_module import CombinatorialFreeModule, CombinatorialFreeModuleElement
 
@@ -274,7 +275,7 @@ def _element_constructor_(self, x):
 
         # If it's a tuple or a list try and create a QuiverPath from it and
         # then return the associated basis element
-        if isinstance(x, (tuple, list, basestring)):
+        if isinstance(x, (tuple, list, six.string_types)):
             return self.monomial(self._semigroup(x))
 
         # Otherwise let CombinatorialFreeModule try

src/sage/quivers/path_semigroup.py

@@ -19,6 +19,7 @@
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 
+import six
 from sage.rings.integer import Integer
 from sage.rings.integer_ring import ZZ
 from sage.structure.parent import Parent
@@ -337,15 +338,15 @@ def _element_constructor_(self, data, check=True):
         elif data == 1:
             start = end = self._quiver.vertex_iterator().next()
             path = []
-        elif isinstance(data, basestring): # one edge
+        elif isinstance(data, six.string_types): # one edge
             i = L.get(data, None)
             if i is None:
                 raise ValueError("data={!r} is not the label of an edge".format(data))
             start,end,_ = E[i]
             path = [i]
         elif not isinstance(data, (tuple,list)):
             raise TypeError("data={} is not valid. A path must be initialized from either a tuple or a list".format(data))
-        elif isinstance(data[0], basestring):  # a list of labels
+        elif isinstance(data[0], six.string_types):  # a list of labels
             start = L.get(data[0])
             if start is None:
                 raise ValueError("data[0]={!r} is not the label of an edge".format(data[0]))