Update to sagemath 6.8

sagemath-4ti2.patch

@@ -1,16 +1,17 @@
 diff -up src/sage/sandpiles/sandpile.py.orig src/sage/sandpiles/sandpile.py
---- src/sage/sandpiles/sandpile.py.orig	2014-11-18 15:24:27.192127311 -0200
-+++ src/sage/sandpiles/sandpile.py	2014-11-18 15:24:38.049127454 -0200
-@@ -23,8 +23,6 @@ packages.  An alternative is to install
- following variable to the correct path.
- """
+--- src/sage/sandpiles/sandpile.py.orig	2015-10-11 17:41:27.067777358 -0300
++++ src/sage/sandpiles/sandpile.py	2015-10-11 17:41:57.909778539 -0300
+@@ -347,9 +347,6 @@ from sage.rings.arith import falling_fac
+ from sage.rings.all import Integer, PolynomialRing, QQ, ZZ, lcm
+ from sage.symbolic.all import I, pi
  
+-# TODO: remove the following line once 4ti2 functions are removed
 -path_to_zsolve = os.path.join(SAGE_LOCAL,'bin','zsolve')
 -
- r"""
- Sage Sandpiles
- 
-@@ -4096,7 +4094,7 @@ class SandpileDivisor(dict):
+ class Sandpile(DiGraph):
+     """
+     Class for Dhar's abelian sandpile model.
+@@ -5230,7 +5227,7 @@ class SandpileDivisor(dict):
          sign_file.close()
          # compute
          try: