Since release of 5.0, when installing our package on build machines, we get DistributionNotFound. I had to pin to "pytest-runner<5". Otherwise, using:

setup_requires=['pytest-runner'],
tests_require=['pytest', 'pytest-cov', 'coverage', 'requests_mock'],

• pip install '.[dev]'
  Processing /home/vsts/work/1/s
  Complete output from command python setup.py egg_info:
  /usr/share/miniconda/envs/py34/lib/python3.4/distutils/dist.py:260: UserWarning: Unknown distribution option: 'use_scm_version'
  warnings.warn(msg)
  warning: install_lib: 'build/lib' does not exist -- no Python modules to install

  zip_safe flag not set; analyzing archive contents...

  Installed /tmp/pip-k_2kf438-build/.eggs/UNKNOWN-0.0.0-py3.4.egg
  Traceback (most recent call last):
  File "", line 1, in
  File "/tmp/pip-k_2kf438-build/setup.py", line 97, in
  'Documentation': [REDACTED]
  File "/usr/share/miniconda/envs/py34/lib/python3.4/distutils/core.py", line 108, in setup
  _setup_distribution = dist = klass(attrs)
  File "/usr/share/miniconda/envs/py34/lib/python3.4/site-packages/setuptools-27.2.0-py3.4.egg/setuptools/dist.py", line 315, in init
  File "/usr/share/miniconda/envs/py34/lib/python3.4/site-packages/setuptools-27.2.0-py3.4.egg/setuptools/dist.py", line 361, in fetch_build_eggs
  File "/usr/share/miniconda/envs/py34/lib/python3.4/site-packages/setuptools-27.2.0-py3.4.egg/pkg_resources/init.py", line 854, in resolve
  pkg_resources.DistributionNotFound: The 'pytest-runner' distribution was not found and is required by the application