Add support for Python 3.9 (#307)

* Add support for Python 3.9

* use conda-forge channel when creating conda envs

currently, python 3.9 is only available of conda-forge

* Update .travis.yml

* fix pandera-core env installation

* add pylint disable exception for python 3.9

* fix unit test: use `set` instead of set literal

* remove python 3.9, pandas 0.25.3 from travis ci

- python 3.9 doesn't support pandas 0.25.3

Co-authored-by: Niels Bantilan <niels.bantilan@gmail.com>

.travis.yml

@@ -20,6 +20,7 @@ env:
   - PYTHON_VERSION=3.6 ENV_FILE=ci/environment_pandas_latest.yml
   - PYTHON_VERSION=3.7 ENV_FILE=ci/environment_pandas_latest.yml
   - PYTHON_VERSION=3.8 ENV_FILE=ci/environment_pandas_latest.yml
+  - PYTHON_VERSION=3.9 ENV_FILE=ci/environment_pandas_latest.yml
   - PYTHON_VERSION=3.6 ENV_FILE=ci/environment_pandas_0_25_3.yml
   - PYTHON_VERSION=3.7 ENV_FILE=ci/environment_pandas_0_25_3.yml
   - PYTHON_VERSION=3.8 ENV_FILE=ci/environment_pandas_0_25_3.yml
@@ -74,7 +75,8 @@ install:
   - |
     conda create -n pandera python=$PYTHON_VERSION || exit 1
     conda env update -n pandera -f $ENV_FILE
-    conda create -n pandera-core python=$PYTHON_VERSION pytest
+    conda create -n pandera-core python=$PYTHON_VERSION || exit 1
+    conda env update -n pandera-core -f $ENV_FILE
     conda list
   - source activate pandera && pip install .[all]
   - source activate pandera-core && pip install .
@@ -91,7 +93,13 @@ script:
   - isort --line-length=79 --check-only pandera tests
   - black --line-length=79 --check pandera tests
   # Linting
-  - pylint pandera tests
+  - |
+    if [ "${PYTHON_VERSION}" == "3.9" ]; then
+        # https://github.com/PyCQA/pylint/issues/776
+        pylint pandera tests --disable=unsubscriptable-object
+    else
+        pylint pandera tests
+    fi
   # Type checking
   - mypy pandera tests
   # Tests

setup.py

@@ -57,6 +57,7 @@
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
         'Topic :: Scientific/Engineering'
         ],