Conditional Pillow install with atests
Latest Pillow versions are Python 3.5+ only. Also little cleanup to
atest/requirements.txt in general.
# See atest/README.rst for more information.
enum34; python_version < '3.0'
-pillow; platform_system == 'Windows'
+pillow < 6; platform_system == 'Windows' and python_version <= '3.4'
+pillow; platform_system == 'Windows' and python_version >= '3.5'
# https://github.com/IronLanguages/ironpython2/issues/113
docutils >= 0.9; platform_python_implementation != 'IronPython'
@@ -15,4 +16,4 @@ pyyaml==5.2; platform_python_implementation == 'Jython'
# On Linux installing lxml with pip may require compilation and development
# headers. Alternatively it can be installed using a package manager like
# `sudo apt-get install python-lxml`.
-lxml; platform_python_implementation == 'CPython' or platform_python_implementation == 'PyPy' and platform_system != 'Windows'
+lxml; platform_python_implementation == 'CPython' or platform_python_implementation == 'PyPy'
