Free/Braid groups not working

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Hi, I am working with SageMath 8.1, and it seems like "FreeGroup()" (and as a consequence BraidGroup() ) are not working properly. If I write in the notebook

G.<a,b,c> = FreeGroup()

I get the following:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "_sage_input_7.py", line 10, in <module>
exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8 -*-\\n" + _support_.preparse_worksheet_cell(base64.b64decode("Ry48YSxiLGM+ID0gRnJlZUdyb3VwKCk="),globals())+"\\n"); execfile(os.path.abspath("___code___.py"))
File "", line 1, in <module>

File "/tmp/tmpFDI_RE/___code___.py", line 2, in <module>
exec compile(u"G = FreeGroup(names=('a', 'b', 'c',)); (a, b, c,) = G._first_ngens(3)" + '\n', '', 'single')
File "", line 1, in <module>

File "sage/misc/lazy_import.pyx", line 388, in sage.misc.lazy_import.LazyImport.__call__ (build/cythonized/sage/misc/lazy_import.c:4118)
File "/usr/lib/python2.7/dist-packages/sage/groups/free_group.py", line 648, in FreeGroup
return FreeGroup_class(names)
 File "sage/misc/classcall_metaclass.pyx", line 330, in sage.misc.classcall_metaclass.ClasscallMetaclass.__call__ (build/cythonized/sage/misc/classcall_metaclass.c:1481)
 File "sage/misc/cachefunc.pyx", line 1059, in sage.misc.cachefunc.CachedFunction.__call__ (build/cythonized/sage/misc/cachefunc.c:6162)
  File "/usr/lib/python2.7/dist-packages/sage/structure/unique_representation.py", line 1021, in __classcall__
instance = typecall(cls, *args, **options)
 File "sage/misc/classcall_metaclass.pyx", line 497, in sage.misc.classcall_metaclass.typecall (build/cythonized/sage/misc/classcall_metaclass.c:1931)
 File "/usr/lib/python2.7/dist-packages/sage/groups/free_group.py", line 736, in __init__
libgap_free_group = libgap.FreeGroup(generator_names)
 File "sage/libs/gap/element.pyx", line 2213, in sage.libs.gap.element.GapElement_Function.__call__ (build/cythonized/sage/libs/gap/element.c:17671)
ValueError: libGAP: Error, FreeGroup: function is not yet defined

Am I doing something wrong? Thanks!