Require python >= 3.7

[maxnoe]

This adresses #1466 , so dropping 3.6 for the next release.

There was also a bug in ci/install.sh resulting in not installing the correct python version for conda builds (so we didn't even test on 3.6 since conda switched to 3.7 by default)

[codecov]

Codecov Report

Merging #1467 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1467      +/-   ##
==========================================
- Coverage   91.17%   91.17%   -0.01%     
==========================================
  Files         183      183              
  Lines       12830    12871      +41     
==========================================
+ Hits        11698    11735      +37     
- Misses       1132     1136       +4     

Impacted Files	Coverage Δ
ctapipe/calib/camera/calibrator.py	94.44% <0.00%> (-4.05%)	⬇️
ctapipe/calib/camera/tests/test_calibrator.py	100.00% <0.00%> (ø)

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[dneise]

There is a timeout in conda env create -n cta-dev --file environment.yml on Travis when building for Py3.8

Is this reason for concern? I restarted the build this morning once .. hoping it was just a mishap on travis.... no luck

[maxnoe]

@dneise it worked yesterday with the first commit... Ah, but that probably was still using the wrong version.

[maxnoe]

It is a missing eventio for python 3.8 I think.

[dneise]

Erm .. I see to be missing the point here ... it is still failing no?

[maxnoe]

Yes, because there is no conda package of eventio for python 3.8. @kosack will upload it shortly.

[dneise]

Ah I see ... thanks