Rollback setup python requirements to master

setup.py

@@ -6,33 +6,33 @@
 
 import isicle
 
-with open('README.md') as f:
+with open("README.md") as f:
     readme = f.read()
 
-with open('LICENSE') as f:
+with open("LICENSE") as f:
     license = f.read()
 
-with open('requirements.txt', 'r') as f:
+with open("requirements.txt", "r") as f:
     install_requires = f.read().splitlines()
 
-pkgs = find_packages(exclude=('examples', 'docs', 'resources'))
+pkgs = find_packages(exclude=("examples", "docs", "resources"))
 
 setup(
-    name='isicle',
+    name="isicle",
     version=isicle.__version__,  # TODO: switch to versioneer.get_version() or alternate method
-    description='ISiCLE: in silico chemical library engine',
+    description="ISiCLE: in silico chemical library engine",
     long_description=readme,
-    long_description_content_type='text/markdown',
-    author='Sean M. Colby',
-    author_email='sean.colby@pnnl.gov',
+    long_description_content_type="text/markdown",
+    author="Sean M. Colby",
+    author_email="sean.colby@pnnl.gov",
     license=license,
     packages=pkgs,
-    python_requires=">3.8",
+    python_requires="==3.9.*",
     install_requires=install_requires,
     classifiers=[
         "Intended Audience :: Science/Research",
         "Topic :: Scientific/Engineering :: Chemistry",
         "Programming Language :: Python :: 3",
-        "License :: OSI Approved :: MIT License"
-    ]
+        "License :: OSI Approved :: MIT License",
+    ],
 )