dropping support for python3.5

Problem with ssl certificate verification.
Tried to set up a PIP_CERT env with downloaded certificate for python3.5, did not solve the problem.

.github/workflows/ci.yml

@@ -19,9 +19,6 @@ jobs:
           - name: py2.7
             os: ubuntu-20.04
             python-version: 2.7
-          - name: py3.5
-            os: ubuntu-20.04
-            python-version: 3.5
           - name: py3.6
             os: ubuntu-20.04
             python-version: 3.6

setup.py

@@ -24,7 +24,7 @@
                     'package1': ['LICENSE', 'README.md']},
       install_requires=['ecdsa>=0.18.0b1'],
       obsoletes=["tlslite"],
-      python_requires=">=2.6, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*",
+      python_requires=">=2.6, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, !=3.5.*",
       classifiers=[
             'Development Status :: 4 - Beta',
             'Intended Audience :: Developers',
@@ -35,7 +35,6 @@
             'Programming Language :: Python :: 2.6',
             'Programming Language :: Python :: 2.7',
             'Programming Language :: Python :: 3',
-            'Programming Language :: Python :: 3.5',
             'Programming Language :: Python :: 3.6',
             'Programming Language :: Python :: 3.7',
             'Programming Language :: Python :: 3.8',