Modernize build system to use setup.cfg

For now, keep but deprecate the requirements/*.txt files.

setup.py

@@ -1,62 +1,16 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
-# © 2015 James R. Barlow: github.com/jbarlow83
+# © 2021 James R. Barlow: github.com/jbarlow83
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 
-from __future__ import print_function, unicode_literals
-
-import sys
-
-from setuptools import find_packages, setup
-
-if sys.version_info < (3, 6):
-    print("Python 3.6 or newer is required", file=sys.stderr)
-    sys.exit(1)
-
-tests_require = open('requirements/test.txt', encoding='utf-8').read().splitlines()
-
-
-def readme():
-    with open('README.md', encoding='utf-8') as f:
-        return f.read()
-
+from setuptools import setup
 
+# Minimal setup to support older setuptools/setuptools_scm
 setup(
-    name='ocrmypdf',
-    description='OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched',
-    long_description=readme(),
-    long_description_content_type='text/markdown',
-    url='https://github.com/jbarlow83/OCRmyPDF',
-    author='James R. Barlow',
-    author_email='james@purplerock.ca',
-    packages=find_packages('src', exclude=["tests", "tests.*"]),
-    package_dir={'': 'src'},
-    keywords=['PDF', 'OCR', 'optical character recognition', 'PDF/A', 'scanning'],
-    classifiers=[
-        "Programming Language :: Python :: 3.6",
-        "Programming Language :: Python :: 3.7",
-        "Programming Language :: Python :: 3.8",
-        "Programming Language :: Python :: 3.9",
-        "Development Status :: 5 - Production/Stable",
-        "Environment :: Console",
-        "Intended Audience :: End Users/Desktop",
-        "Intended Audience :: Science/Research",
-        "Intended Audience :: System Administrators",
-        "License :: OSI Approved :: Mozilla Public License 2.0 (MPL 2.0)",
-        "Operating System :: MacOS :: MacOS X",
-        "Operating System :: Microsoft :: Windows :: Windows 10",
-        "Operating System :: POSIX",
-        "Operating System :: POSIX :: BSD",
-        "Operating System :: POSIX :: Linux",
-        "Topic :: Scientific/Engineering :: Image Recognition",
-        "Topic :: Text Processing :: Indexing",
-        "Topic :: Text Processing :: Linguistic",
-    ],
-    python_requires=' >= 3.6',
     setup_requires=[  # can be removed whenever we can drop pip 9 support
         'cffi >= 1.9.1',  # to build the leptonica module
         'setuptools_scm',  # so that version will work
@@ -64,26 +18,4 @@ setup(
     ],
     use_scm_version={'version_scheme': 'post-release'},
     cffi_modules=['src/ocrmypdf/lib/compile_leptonica.py:ffibuilder'],
-    install_requires=[
-        'cffi >= 1.9.1',  # must be a setup and install requirement
-        'coloredlogs >= 14.0',  # strictly optional
-        'img2pdf >= 0.3.0, < 0.5',  # pure Python, so track HEAD closely
-        'pdfminer.six >= 20191110, != 20200720, <= 20201018',
-        "pikepdf >= 2.10.0",
-        'Pillow >= 8.1.2',
-        'pluggy >= 0.13.0, < 1.0',
-        'reportlab >= 3.5.66',
-        'setuptools',
-        'tqdm >= 4',
-    ],
-    tests_require=tests_require,
-    entry_points={'console_scripts': ['ocrmypdf = ocrmypdf.__main__:run']},
-    package_data={'ocrmypdf': ['data/sRGB.icc', 'py.typed']},
-    include_package_data=True,
-    zip_safe=False,
-    project_urls={
-        'Documentation': 'https://ocrmypdf.readthedocs.io/',
-        'Source': 'https://github.com/jbarlow83/ocrmypdf',
-        'Tracker': 'https://github.com/jbarlow83/ocrmypdf/issues',
-    },
 )