use environments.yml to setup for travis-ci

[prjemian]

The current setup for travis uses conda, then pip. The pip part creates wheels which duplicate much of the conda setup. Use the existing environment.yml file (created for RTD) to setup for travis-ci.

Example: https://travis-ci.org/github/BCDA-APS/apstools/jobs/709523510#L185

[prjemian]

Looking at Line 185 (from above), a pip installation happens BEFORE the miniconda is downloaded and then installed.

[prjemian]

Here is how to create a new conda environment using the environment.yml file:

conda env create -n test -f environment.yml

How to specify the python version (python=$TRAVIS_PYTHON_VERSION) here?

[prjemian]

this does not work

conda env create -n test python=$TRAVIS_PYTHON_VERSION -f environment.yml

Need a CI version of environment.yml that has no python version listed.

[prjemian]

Nope, still gets python 3.8:

(bluesky_2020_5) prjemian@poof ~/.../projects/apstools $ conda env create -n test python=3.7 -f environment-travis.yml
Collecting package metadata (repodata.json): done
Solving environment: done
Preparing transaction: done
Verifying transaction: |
SafetyError: The package for pyqt located at /home/prjemian/Apps/anaconda/pkgs/pyqt-5.9.2-py38h05f1152_4
appears to be corrupted. The path 'plugins/designer/libpyqt5.so'
has an incorrect size.
  reported size: 35656 bytes
  actual size: 35664 bytes

ClobberError: This transaction has incompatible packages due to a shared path.
  packages: defaults/linux-64::python-3.8.3-hcff3b4d_2, defaults/linux-64::markupsafe-1.1.1-py38h7b6447c_0, defaults/linux-64::pymongo-3.9.0-py38he6710b0_0, defaults/linux-64::pyqt-5.9.2-py38h05f1152_4
  path: 'lib/python3.8/__pycache__/_sysconfigdata_x86_64_conda_cos6_linux_gnu.cpython-38.pyc'
# ... installation
(bluesky_2020_5) prjemian@poof ~/.../projects/apstools $ conda list -n test python
# packages in environment at /home/prjemian/Apps/anaconda/envs/test:
#
# Name                    Version                   Build  Channel
ipython                   7.16.1           py38h5ca1d4c_0
ipython_genutils          0.2.0                    py38_0
msgpack-python            1.0.0            py38hfd86e86_1
python                    3.8.3                hcff3b4d_2
python-dateutil           2.8.1                      py_0
python_abi                3.8                      1_cp38    conda-forge

[prjemian]

Need to edit the environment.yml file with the python=$TRAVIS_PYTHON_VERSION requirement.

[prjemian]

Like this:

cp environment.yml environment-travis.yml
sed -i s:python\>=3.6.0:python=\$\{TRAVIS_PYTHON_VERSION\}:g environment-travis.yml

[prjemian]

Before this change, remove the first pip installation.

[prjemian]

Wow! Cut the travis-ci test time in half!