Failing test on 2.1.0

[satta]

The recently released version 2.1.0 does not complete its tests successfully:

======================================================================
FAIL: test_robinson_foulds_convergence (test_external_dependancies.TestExternalDependancies)
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Traceback (most recent call last):
  File "/vagrant/gubbins/python/gubbins/tests/test_external_dependancies.py", line 82, in test_robinson_foulds_convergence
    assert common.GubbinsCommon.has_tree_been_seen_before(['RAxML_result.multiple_recombinations.iteration_1','RAxML_result.multiple_recombinations.iteration_2','RAxML_result.multiple_recombinations.iteration_3','RAxML_result.multiple_recombinations.iteration_4','RAxML_result.multiple_recombinations.iteration_5','RAxML_result.multiple_recombinations.iteration_6','RAxML_result.multiple_recombinations.iteration_7','RAxML_result.multiple_recombinations.iteration_8','RAxML_result.multiple_recombinations.iteration_9','RAxML_result.multiple_recombinations.iteration_10','multiple_recombinations.final_tree.tre'],'robinson_foulds') == 1
AssertionError

I've been running the tests on Debian stretch, using RaXML 8.2.8.

[tseemann]

@satta can you close this issue given https://github.com/sanger-pathogens/gubbins/releases/tag/v2.3.4