[tor-bugs] #22998 [Obfuscation/BridgeDB]: Update BridgeDB's .travis.yml to run tests for Debian buster dependency versions

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#22998: Update BridgeDB's .travis.yml to run tests for Debian buster dependency
versions
--------------------------------------+-----------------------------
     Reporter:  isis                  |      Owner:  isis
         Type:  defect                |     Status:  new
     Priority:  Medium                |  Milestone:
    Component:  Obfuscation/BridgeDB  |    Version:
     Severity:  Normal                |   Keywords:  bridgedb-ci, ci
Actual Points:                        |  Parent ID:
       Points:  .5                    |   Reviewer:
      Sponsor:                        |
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 weasel updated polyanthum today to Debian stretch. In keeping with running
 BridgeDB's CI with the currently used versions of Twisted and PyOpenSSL as
 well as the versions slated for the next Debian release, we'll need to
 update some version numbers.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22998>
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