sage: move sympow cache to .sage

pkgs/applications/science/math/sage/patches/sympow-cache.patch

@@ -0,0 +1,21 @@
+diff --git a/src/sage/lfunctions/sympow.py b/src/sage/lfunctions/sympow.py
+index 1640ac4f6a..03578be7b8 100644
+--- a/src/sage/lfunctions/sympow.py
++++ b/src/sage/lfunctions/sympow.py
+@@ -50,6 +50,7 @@ from __future__ import print_function, absolute_import
+ 
+ import os
+ 
++from sage.env import DOT_SAGE
+ from sage.structure.sage_object import SageObject
+ from sage.misc.all import pager, verbose
+ import sage.rings.all
+@@ -76,7 +77,7 @@ class Sympow(SageObject):
+         """
+         Used to call sympow with given args
+         """
+-        cmd = 'sympow %s'%args
++        cmd = 'env SYMPOW_CACHEDIR="%s/sympow///" sympow %s' % (DOT_SAGE, args)
+         v = os.popen(cmd).read().strip()
+         verbose(v, level=2)
+         return v

pkgs/applications/science/math/sage/sage-src.nix

@@ -100,6 +100,11 @@ stdenv.mkDerivation rec {
       rev = "c11d9cfa23ff9f77681a8f12742f68143eed4504";
       sha256 = "0xzra7mbgqvahk9v45bjwir2mqz73hrhhy314jq5nxrb35ysdxyi";
     })
+
+    # After updating smypow to (https://trac.sagemath.org/ticket/3360) we can
+    # now set the cache dir to be withing the .sage directory. This is not
+    # strictly necessary, but keeps us from littering in the user's HOME.
+    ./patches/sympow-cache.patch
   ];
 
   patches = nixPatches ++ bugfixPatches ++ packageUpgradePatches;