Drop testing of Python 3.5

Due to message from CI:

DEPRECATION: Python 3.5 reached the end of its life on September 13th,
2020. Please upgrade your Python as Python 3.5 is no longer maintained.
pip 21.0 will drop support for Python 3.5 in January 2021. pip 21.0 will
remove support for this functionality.

.github/workflows/pythonpackage.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8]
 
     steps:
     - uses: actions/checkout@v2

docs/manpage.rst

@@ -11,7 +11,7 @@ Description
 -----------
 :program:`sshuttle` allows you to create a VPN connection from your
 machine to any remote server that you can connect to via
-ssh, as long as that server has python 3.5 or higher.
+ssh, as long as that server has python 3.6 or higher.
 
 To work, you must have root access on the local machine,
 but you can have a normal account on the server.

docs/requirements.rst

@@ -6,7 +6,7 @@ Client side Requirements
 
 - sudo, or root access on your client machine.
   (The server doesn't need admin access.)
-- Python 3.5 or greater.
+- Python 3.6 or greater.
 
 
 Linux with NAT method
@@ -70,7 +70,7 @@ cmd.exe with Administrator access. See :doc:`windows` for more information.
 Server side Requirements
 ------------------------
 
-- Python 3.5 or greater.
+- Python 3.6 or greater.
 
 
 Additional Suggested Software

setup.py

@@ -49,7 +49,6 @@ setup(
         "License :: OSI Approved :: "
             "GNU Lesser General Public License v2 or later (LGPLv2+)",
         "Operating System :: OS Independent",
-        "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
@@ -61,7 +60,7 @@ setup(
             'sshuttle = sshuttle.cmdline:main',
         ],
     },
-    python_requires='>=3.5',
+    python_requires='>=3.6',
     install_requires=[
         'psutil',
     ],