mathics: Fix unit tests

Disabled two tests that require a preinstalled build of Mathics to
work, which is incompatible with the way nix runs them.

[Bjørn: remove unrelated disabling on Python 3]

pkgs/development/python-modules/mathics/disable_console_tests.patch

@@ -0,0 +1,21 @@
+These tests require that Mathics already be installed to work,
+which is not true when nix runs them.
+
+--- a/test/test_console.py	2015-09-07 21:41:08.530501979 -0700
++++ b/test/test_console.py	2015-09-07 21:42:44.082176084 -0700
+@@ -13,6 +13,7 @@
+         os.environ["TERM"] = "dumb"
+         self.console = pexpect.spawn('python2 mathics/main.py --color NOCOLOR')
+ 
++    @unittest.expectedFailure
+     def testLaunch(self):
+         cons = self.console
+ 
+@@ -41,6 +42,7 @@
+             'Quit by pressing CONTROL-D\r\n'
+             '\r\n')
+ 
++    @unittest.expectedFailure
+     def testPrompt(self):
+         cons = self.console
+         cons.expect('Quit by pressing CONTROL-D\r\n\r\n')

pkgs/top-level/python-packages.nix

@@ -7912,6 +7912,8 @@ let
       sha256 = "1hyrxnhxw35vn00k55hp9bkg8vg4dsphrpfg1yg4cn53y78rk1im";
     };
 
+    patches = [ ../development/python-modules/mathics/disable_console_tests.patch ];
+
     buildInputs = with self; [ pexpect ];
 
     propagatedBuildInputs = with self; [