Add flake check to travis (#2632)

* add flake check to travis

* only flake xarray

* flake changes

* rename flake -> flake8 in travis config

Author: max-sixty

.travis.yml

@@ -32,6 +32,7 @@ matrix:
   - env: CONDA_ENV=py36-rasterio
   - env: CONDA_ENV=py36-zarr-dev
   - env: CONDA_ENV=docs
+  - env: CONDA_ENV=flake8
   - env: CONDA_ENV=py36-hypothesis
 
   allow_failures:
@@ -62,6 +63,8 @@ before_install:
 install:
   - if [[ "$CONDA_ENV" == "docs" ]]; then
       conda env create -n test_env --file doc/environment.yml;
+    elif [[ "$CONDA_ENV" == "flake8" ]]; then
+      conda env create -n test_env --file ci/requirements-py37.yml;
     else
       conda env create -n test_env --file ci/requirements-$CONDA_ENV.yml;
     fi
@@ -77,6 +80,8 @@ script:
   - if [[ "$CONDA_ENV" == "docs" ]]; then
       conda install -c conda-forge sphinx sphinx_rtd_theme sphinx-gallery numpydoc;
       sphinx-build -n -j auto -b html -d _build/doctrees doc _build/html;
+    elif [[ "$CONDA_ENV" == "flake8" ]]; then
+      flake8 xarray ;
     elif [[ "$CONDA_ENV" == "py36-hypothesis" ]]; then
       pytest properties ;
     else

xarray/core/pdcompat.py

@@ -39,7 +39,6 @@
 
 
 import numpy as np
-import pandas as pd
 
 
 # for pandas 0.19

xarray/tests/test_dataarray.py

@@ -1028,7 +1028,7 @@ def test_sel(lab_indexer, pos_indexer, replaced_idx=False,
         assert_identical(mdata.sel(x={'one': 'a', 'two': 1}),
                          mdata.sel(one='a', two=1))
 
-    def test_selection_multiindex(self):
+    def test_selection_multiindex_remove_unused(self):
         # GH2619. For MultiIndex, we need to call remove_unused.
         ds = xr.DataArray(np.arange(40).reshape(8, 5), dims=['x', 'y'],
                           coords={'x': np.arange(8), 'y': np.arange(5)})