Altera instalação dos requirements e corrige para pip 20.1.x

setup.py

@@ -1,11 +1,5 @@
 #!/usr/bin/env python
 import setuptools
-try:  # for pip >= 10
-    from pip._internal.req import parse_requirements as parse
-except ImportError:  # for pip <= 9.0.3
-    from pip.req import parse_requirements as parse
-
-requirements = lambda f: [str(i.req) for i in parse(f, session=False)]
 
 setuptools.setup(
     name='PyNFe',
@@ -17,7 +11,12 @@ setuptools.setup(
     package_data={
         'pynfe': ['data/**/*.txt'],
     },
-    install_requires=requirements('requirements.txt'),
+    install_requires=[
+        'pyopenssl',
+        'requests',
+        'lxml',
+        'signxml',
+    ],
     zip_safe=False,
     python_requires='>=3.6',
 )