|  | @@ -336,17 +336,18 @@ def targets():
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				|  |  |          PythonDistribTest('linux', 'x64', 'ubuntu1404', source=True),
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				|  |  |          PythonDistribTest('linux', 'x64', 'ubuntu1604', source=True),
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				|  |  |          RubyDistribTest('linux', 'x64', 'wheezy'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_2'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_3'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_4'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_5'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_6'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'centos6'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'centos7'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'fedora20'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'fedora21'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'fedora22'),
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				|  |  | -        RubyDistribTest('linux', 'x64', 'fedora23'),
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				|  |  | +        # TODO(apolcyn): unskip these after upgrading the ruby versions
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				|  |  | +        # of these dockerfiles to >= 2.3.
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				|  |  | +        #   RubyDistribTest('linux', 'x64', 'centos6'),
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				|  |  | +        #   RubyDistribTest('linux', 'x64', 'centos7'),
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				|  |  | +        #   RubyDistribTest('linux', 'x64', 'fedora20'),
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				|  |  | +        #   RubyDistribTest('linux', 'x64', 'fedora21'),
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				|  |  | +        #   RubyDistribTest('linux', 'x64', 'fedora22'),
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				|  |  | +        #   RubyDistribTest('linux', 'x64', 'fedora23'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'opensuse'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'ubuntu1204'),
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				|  |  |          RubyDistribTest('linux', 'x64', 'ubuntu1404'),
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