When running doctests, use the current_randstate()'s seed for Interfa…

…ce.rand_seed()

This allows pexpect Interfaces that set some random seed to use a consistent,
predictable value for tests rather than being completely arbitrary.

src/sage/interfaces/interface.py

@@ -133,8 +133,16 @@ def rand_seed(self):
  sage: s.rand_seed() # random
  365260051L
  """
- from sage.misc.randstate import randstate
- return randstate().seed()&0x1FFFFFFF
+ import sage.doctest
+ if sage.doctest.DOCTEST_MODE:
+ # set the random seed through the current randstate
+ from sage.misc.randstate import current_randstate
+ seed = current_randstate().seed()
+ else:
+ from sage.misc.randstate import randstate
+ seed = randstate().seed()
+
+ return seed & 0x1FFFFFFF
 
  def set_seed(self, seed=None):
  """