sage: fix transient ecl error (#54285)

Sometimes the doctests fail because ecl races to create a directory.
This should fix that by making sure each process has its own directory.

pkgs/applications/science/math/sage/patches/fix-ecl-race.patch

@@ -0,0 +1,19 @@
+diff --git a/src/sage/doctest/forker.py b/src/sage/doctest/forker.py
+index 02e18e67e7..2ebf6eb35f 100644
+--- a/src/sage/doctest/forker.py
++++ b/src/sage/doctest/forker.py
+@@ -1075,6 +1075,14 @@ class SageDocTestRunner(doctest.DocTestRunner, object):
+             sage: set(ex2.predecessors) == set([ex0,ex1])
+             True
+         """
++
++        # Fix ECL dir race conditions by using a separate dir for each process
++        # (https://trac.sagemath.org/ticket/26968)
++        os.environ['MAXIMA_USERDIR'] = "{}/sage-maxima-{}".format(
++            tempfile.gettempdir(),
++            os.getpid()
++        )
++
+         if isinstance(globs, RecordingDict):
+             globs.start()
+         example.sequence_number = len(self.history)

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

@@ -46,6 +46,9 @@ stdenv.mkDerivation rec {
     # tests) are also run. That is necessary to test dochtml individually. See
     # https://trac.sagemath.org/ticket/26110 for an upstream discussion.
     ./patches/Only-test-py2-py3-optional-tests-when-all-of-sage-is.patch
+
+    # Fixes a potential race condition which can lead to transient doctest failures.
+    ./patches/fix-ecl-race.patch
   ];
 
   # Patches needed because of package updates. We could just pin the versions of