Update to sagemath 8.7.

- Drop upstreamed -giac patch.
- Add -sagetex patch to fix a python indentation error.
- Add -rubiks patch to fix compilation of the rubiks library.
- Add -random patch to fix a non-random random bit generator.
- Drop pip3 workaround; the binary is now named just pip again.

sagemath-latte.patch

@@ -1,7 +1,7 @@
 diff -up src/sage/interfaces/latte.py.orig src/sage/interfaces/latte.py
---- src/sage/interfaces/latte.py.orig	2019-01-16 09:44:45.946769879 -0700
-+++ src/sage/interfaces/latte.py	2019-01-16 09:47:33.355765786 -0700
-@@ -112,7 +112,7 @@ def count(arg, ehrhart_polynomial=False,
+--- src/sage/interfaces/latte.py.orig	2019-04-08 12:05:07.092855841 -0600
++++ src/sage/interfaces/latte.py	2019-04-08 13:37:31.377803169 -0600
+@@ -113,7 +113,7 @@ def count(arg, ehrhart_polynomial=False,
      # Check that LattE is present
      Latte().require()
  
@@ -10,9 +10,9 @@ diff -up src/sage/interfaces/latte.py.orig src/sage/interfaces/latte.py
      if ehrhart_polynomial and multivariate_generating_function:
          raise ValueError
      if ehrhart_polynomial:
-@@ -305,7 +305,7 @@ def integrate(arg, polynomial=None, algo
-     # Check that LattE is present
-     Latte().require()
+@@ -308,7 +308,7 @@ def integrate(arg, polynomial=None, algo
+ 
+     from sage.rings.rational import Rational
  
 -    args = ['integrate']
 +    args = ['latte-integrate']