Drop support for Python 3.6

.travis.yml

@@ -6,7 +6,6 @@ cache: pip
 # See: https://github.com/travis-ci/travis-ci/issues/3024
 
 python:
-  - "3.6"
   - "3.7"
   - "3.8"
   - "3.9"

README.md

@@ -64,13 +64,8 @@ index-servers =
 
 ```
 . ./.venv/bin/activate
-pip install twine
 
 poetry build
 twine check dist/rsa-4.9.tar.gz dist/rsa-4.9-*.whl
 twine upload -r rsa dist/rsa-4.9.tar.gz dist/rsa-4.9-*.whl
 ```
-
-The `pip install twine` is necessary as Python-RSA requires Python >= 3.6, and
-Twine requires at least version 3.7. This means Poetry refuses to add it as
-dependency.

doc/installation.rst

@@ -25,7 +25,7 @@ GitHub. It also hosts the `issue tracker`_.
 Dependencies
 ------------
 
-Python-RSA is compatible with Python versions 3.5 and newer. The last
+Python-RSA is compatible with Python versions 3.7 and newer. The last
 version with Python 2.7 support was Python-RSA 4.0.
 
 Python-RSA has very few dependencies. As a matter of fact, to use it

pyproject.toml

@@ -16,7 +16,6 @@ classifiers = [
   "Operating System :: OS Independent",
   "Programming Language :: Python",
   "Programming Language :: Python :: 3",
-  "Programming Language :: Python :: 3.6",
   "Programming Language :: Python :: 3.7",
   "Programming Language :: Python :: 3.8",
   "Programming Language :: Python :: 3.9",
@@ -32,7 +31,7 @@ include = [
 ]
 
 [tool.poetry.dependencies]
-python = ">=3.6, <4"
+python = ">=3.7, <4"
 pyasn1 = ">=0.1.3"
 
 [tool.poetry.dev-dependencies]

tests/test_pkcs1.py

@@ -101,7 +101,6 @@ def test_sign_verify(self):
         signature = pkcs1.sign(message, self.priv, "SHA-256")
         self.assertEqual("SHA-256", pkcs1.verify(message, signature, self.pub))
 
-    @unittest.skipIf(sys.version_info < (3, 6), "SHA3 requires Python 3.6+")
     def test_sign_verify_sha3(self):
         """Test happy flow of sign and verify with SHA3-256"""
 

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 # Environment changes have to be manually synced with '.travis.yml'.
-envlist = py36,py37,py38,py39,py310
+envlist = py37,py38,py39,py310
 isolated_build = True
 
 [pytest]