fix doctests in permutation_group.py

Author: dimpase

src/sage/groups/perm_gps/permgroup.py

@@ -681,6 +681,13 @@ def gap(self):
             sage: UPG = PG.subgroup([p1, p2, p3, p4, p5], canonicalize=False)
             sage: UPG.gap()
             <permutation group with 5 generators>
+
+        the caching of _libgap_() works::
+
+            sage: S = SymmetricGroup(4)
+            sage: g1 = S._libgap_()
+            sage: g1.IsIdenticalObj(S._libgap_())
+            true
         """
         if self._libgap is not None:
             return self._libgap
@@ -1822,8 +1829,8 @@ def stabilizer(self, point, action="OnPoints"):
             sage: G = PermutationGroup([[(1,2),(3,4)], [(1,2,3,4,10)]])
             sage: G.stabilizer(10)
             Subgroup generated by [(2,3,4), (1,2)(3,4)] of (Permutation Group with generators [(1,2)(3,4), (1,2,3,4,10)])
-            sage: G.stabilizer(1)
-            Subgroup generated by [(2,3)(4,10), (2,10,3)] of (Permutation Group with generators [(1,2)(3,4), (1,2,3,4,10)])
+            sage: G.stabilizer(1) == G.subgroup(['(2,3)(4,10)', '(2,10,3)'])
+            True
             sage: G = PermutationGroup([[(2,3,4)],[(6,7)]])
             sage: G.stabilizer(1)
             Subgroup generated by [(6,7), (2,3,4)] of (Permutation Group with generators [(6,7), (2,3,4)])
@@ -1984,7 +1991,9 @@ def strong_generating_system(self, base_of_group=None, implementation="sage"):
             sage: G = PermutationGroup([[(1,2,3,4)],[(1,2)]])
             sage: G.strong_generating_system()
             [[(), (1,2)(3,4), (1,3)(2,4), (1,4)(2,3)],
-             [(), (2,4), (2,3,4)], [(), (3,4)], [()]]
+            [(), (2,4,3), (2,3,4)],
+            [(), (3,4)],
+            [()]]
             sage: G = PermutationGroup([[(1,2,3)],[(4,5,7)],[(1,4,6)]])
             sage: G.strong_generating_system()
             [[(), (1,2,3), (1,4,6), (1,3,2), (1,5,7,4,6), (1,6,4), (1,7,5,4,6)],