Hide GAP finiteness warnings during isomorphism check

src/sage/groups/cubic_braid.py

@@ -640,7 +640,6 @@ class CubicBraidGroup(UniqueRepresentation, FinitelyPresentedGroup):
         sage: C3.gens()
         (t0, t1)
         sage: U3.is_isomorphic(C3)
-        #I  Forcing finiteness test
         True
         sage: U3.as_classical_group()
         Subgroup generated by [(1,7,6)(3,19,14)(4,15,10)(5,11,18)(12,16,20),
@@ -1604,7 +1603,6 @@ def as_permutation_group(self, use_classical=True):
             sage: C3 = CubicBraidGroup(3)
             sage: PC3 = C3.as_permutation_group()
             sage: assert C3.is_isomorphic(PC3)  # random (with respect to the occurrence of the info message)
-            #I  Forcing finiteness test
             sage: PC3.degree()
             8
             sage: c = C3([2,1-2])

src/sage/groups/finitely_presented.py

@@ -1080,7 +1080,6 @@ def direct_product(self, H, reduced=False, new_names=True):
             sage: C7 = G / [G.0**7]; C6 =  G / [G.0**6]
             sage: C14 = G / [G.0**14]; C3 =  G / [G.0**3]
             sage: C7.direct_product(C6).is_isomorphic(C14.direct_product(C3))
-            #I  Forcing finiteness test
             True
             sage: F = FreeGroup(2); D = F / [F([1,1,1,1,1]),F([2,2]),F([1,2])**2]
             sage: D.direct_product(D).as_permutation_group().is_isomorphic(
@@ -1174,7 +1173,6 @@ def semidirect_product(self, H, hom, check=True, reduced=False):
             sage: alpha = (Q.gens(), [a,b])
             sage: S2 = C2.semidirect_product(Q, ([C2.0],[alpha]))
             sage: S1.is_isomorphic(S2)
-            #I  Forcing finiteness test
             True
 
         Dihedral groups can be constructed as semidirect products
@@ -1233,8 +1231,6 @@ def semidirect_product(self, H, hom, check=True, reduced=False):
             sage: Se2 =  D.semidirect_product(C ,id2)
             sage: Dp1 = C.direct_product(D)
             sage: Dp1.is_isomorphic(Se1), Dp1.is_isomorphic(Se2)
-            #I  Forcing finiteness test
-            #I  Forcing finiteness test
             (True, True)
 
         Most checks for validity of input are left to GAP to handle::

src/sage/groups/finitely_presented_named.py

@@ -451,7 +451,6 @@
         sage: Q.order(), Q.is_abelian()
         (8, False)
         sage: Q.is_isomorphic(groups.presentation.DiCyclic(2))
-        #I  Forcing finiteness test
         True
     """
     F = FreeGroup(['a','b'])
@@ -490,7 +489,7 @@
         (True, 1)
         sage: A3 = groups.presentation.Alternating(3); A3.order(), A3.as_permutation_group().is_cyclic()
         (3, True)
         sage: A8 = groups.presentation.Alternating(8); A8.order()
         20160
     """
     from sage.groups.perm_gps.permgroup_named import AlternatingGroup
@@ -554,12 +553,6 @@
         ....:     P = groups.presentation.BinaryDihedral(n)
         ....:     M = groups.matrix.BinaryDihedral(n)
         ....:     assert P.is_isomorphic(M)
-        #I  Forcing finiteness test
-        #I  Forcing finiteness test
-        #I  Forcing finiteness test
-        #I  Forcing finiteness test
-        #I  Forcing finiteness test
-        #I  Forcing finiteness test
     """
     F = FreeGroup('x,y,z')
     x,y,z = F.gens()

src/sage/groups/libgap_mixin.py

@@ -946,4 +946,16 @@ def is_isomorphic(self, H):
             sage: F == G, G == H, F == H
             (False, False, False)
         """
-        return self.gap().IsomorphismGroups(H.gap()) != libgap.fail
+        # If GAP doesn't know that the groups are finite, it will
+        # check. This emits an informational warning, and then
+        # annotates the groups as being finite (assuming they were) so
+        # that future isomorphism checks are silent. This can lead to
+        # apparent non-determinism in the output as statements are
+        # rearranged. There's nothing the user can do about this
+        # anyway, and it happens in trivial cases like the alternating
+        # group on one element, so we prefer to hide the warning.
+        old_warnlevel = libgap.InfoLevel(libgap.InfoWarning)
+        libgap.SetInfoLevel(libgap.InfoWarning, 0)
+        result = self.gap().IsomorphismGroups(H.gap()) != libgap.fail
+        libgap.SetInfoLevel(libgap.InfoWarning, old_warnlevel)
+        return result

src/sage/schemes/curves/projective_curve.py

@@ -1400,7 +1400,7 @@
             sage: set_verbose(-1)
             sage: P.<x,y,z> = ProjectiveSpace(QQ, 2)
             sage: C = Curve([(x^2 + y^2 - y*z - 2*z^2)*(y*z - x^2 + 2*z^2)*z + y^5], P)
             sage: C.ordinary_model() # long time (5 seconds)
             Scheme morphism:
               From: Projective Plane Curve over Number Field in a
                     with defining polynomial y^2 - 2 defined
@@ -1805,7 +1805,6 @@
             ....:             + (x-18*z)*(z^2+11*x*z-x^2)^2)
             sage: G0 = C.fundamental_group()                    # needs sirocco
             sage: G.is_isomorphic(G0)                           # needs sirocco
-            #I  Forcing finiteness test
             True
             sage: C = P.curve(z)
             sage: C.fundamental_group()                         # needs sirocco