chore: bump required treetime version to 0.8.0

[rneher]

Description of proposed changes

not much has changed in treetime but I dropped python 2.7. So new middle digit.

Thank you for contributing to Nextstrain!

[codecov]

Codecov Report

Merging #633 (6b9cc9c) into master (d2d5423) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #633   +/-   ##
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  Coverage   28.68%   28.68%           
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  Files          39       39           
  Lines        5389     5389           
  Branches     1326     1326           
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  Hits         1546     1546           
  Misses       3785     3785           
  Partials       58       58           

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[huddlej]

This works for me. Thanks, @rneher!

Do you have an example of how to get the Nexus export error for BioPython? Can I just install TreeTime, force install the latest BioPython, and then run the TreeTime test suite?

[rneher]

I made an issue with an example:

biopython/biopython#3361

and also a PR that fixes it....

biopython/biopython#3366

[huddlej]

Wow, that was fast! Thank you! Merging this now. I'll make a new Augur release with this change this morning.