Simplify travis CI, update pytest / cov, add caching for pip (#225)

Similar commit in unihan-etl:
- cihai/unihan-etl@051bd6d
- cihai/unihan-etl#196

More into on setup.py test being removed:
- http://doc.pytest.org/en/5.3.2/changelog.html#pytest-3-6-2-2018-06-20
- pytest-dev/pytest#3552

.travis.yml

@@ -1,21 +1,15 @@
 language: python
 sudo: false
+dist: bionic  # 18.04
 if: (type = push AND branch IN (master)) OR (type = pull_request)
 python:
   - 2.7
-  - 3.6
   - 3.7
-  - pypy
   - pypy3
-before_install:
-  - export PIP_USE_MIRRORS=true
-  - pip install -U pip setuptools
-  - pip install -U pytest mock # https://github.com/travis-ci/travis-ci/issues/4873
-  - pip install coveralls
-  - git config --global user.name 'travis-ci'
-  - git config --global user.email '[email protected]'
+cache: pip
 install:
-  - "pip install -e ."
-script: coverage run --source=unihan_db setup.py test
+  - pip install -e .
+  - pip install -r requirements/test.txt
+script: py.test --cov=unihan_db
 after_success:
   - bash <(curl -s https://codecov.io/bash)

Pipfile

@@ -11,6 +11,8 @@ flake8 = "*"
 pytest = "*"
 unihan-db = {path = ".",editable = true}
 sphinx-issues = "*"
+pytest-cov = "*"
+coverage = "*"
 
 [packages]
 appdirs = "*"

requirements/test.txt

@@ -1 +1,3 @@
-pytest<=5.1
+pytest<6
+pytest-cov
+coverage

setup.py

@@ -5,7 +5,6 @@
 import sys
 
 from setuptools import setup
-from setuptools.command.test import test as TestCommand
 
 about = {}
 with open("unihan_db/__about__.py") as fp:
@@ -25,20 +24,6 @@
 history = open('CHANGES').read().replace('.. :changelog:', '')
 
 
-class PyTest(TestCommand):
-    user_options = [('pytest-args=', 'a', "Arguments to pass to py.test")]
-
-    def initialize_options(self):
-        TestCommand.initialize_options(self)
-        self.pytest_args = []
-
-    def run_tests(self):
-        import pytest
-
-        errno = pytest.main(self.pytest_args)
-        sys.exit(errno)
-
-
 setup(
     name=about['__title__'],
     version=about['__version__'],
@@ -57,7 +42,6 @@ def run_tests(self):
     include_package_data=True,
     install_requires=install_reqs,
     tests_require=tests_reqs,
-    cmdclass={'test': PyTest},
     zip_safe=False,
     keywords=about['__title__'],
     packages=['unihan_db'],