[MacPorts] #54376: math/gsl documentation variant now depends on Sphinx

[MacPorts]

#54376: math/gsl documentation variant now depends on Sphinx
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  Reporter:  slewsys  |      Owner:  dtakahashi
      Type:  defect   |     Status:  assigned
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:
      Port:  gsl      |
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Comment (by Schamschula):

 I just created new variants for Python 2.7, 3.5 and 3.6 versions of
 Sphinx. One of those is required to build the documentation.

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Ticket URL: <https://trac.macports.org/ticket/54376#comment:7>
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