[MacPorts] #39068: py-mysql: add +mariadb and +percona variants

[MacPorts]

#39068: py-mysql: add +mariadb and +percona variants
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  Reporter:  newberg@…    |      Owner:  rwilcox@…
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  py-mysql     |
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Comment (by ryandesign@…):

 A +mysql56 variant should also be added.

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Ticket URL: <https://trac.macports.org/ticket/39068#comment:2>
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