Requires Python 3.6, configures tox for testing different Python versions

.gitignore

@@ -1,2 +1,6 @@
 __pycache__
 .mypy_cache
+.tox
+/*.egg-info
+/dist
+/build

README.md

@@ -24,6 +24,17 @@ user@server:~$ linkulator
 Enter a category ID, p to post a link, s to search, or q to quit: 
 ```
 
+## Prerequisites
+
+Linkulator requires Python 3.6.9 or greater. If you use an earlier version, you may get the following error:
+
+```shell
+  File "./linkulator.py", line 21
+    link_data: list = LinkData.link_data
+             ^
+SyntaxError: invalid syntax
+```
+
 ## Installation
 
 Just clone this repo into any location in users' paths.  Each user can have their own copy, in case they want to customize it, or you can install a central version in /usr/local/bin.

linkulator.py

@@ -446,18 +446,6 @@ def signal_handler(sig, frame):
 
 def main():
     """main function - handles argument parsing and calls menu system"""
-
-    low_py_ver = 3.6
-    py_ver = str(sys.version_info[0]) + "." + str(sys.version_info[1])
-    py_ver = float(py_ver)
-    if py_ver < low_py_ver:
-        raise Exception(
-            "Must be using Python "
-            + str(low_py_ver)
-            + " or higher.  Instead you're using "
-            + str(py_ver)
-        )
-
     signal.signal(signal.SIGINT, signal_handler)
     args = sys.argv[1:]
     config.init()

setup.py

@@ -0,0 +1,22 @@
+from setuptools import setup, find_packages
+
+with open("README.md", "r") as fh:
+    long_description = fh.read()
+
+setup(
+    name="linkulator",
+    version="2.0.0",
+    author="cmccabe",
+    author_email="rawtext.club",
+    description="Linkulator is a command line link aggregator; somewhat like news.ycombinator.com, or lobste.rs, but simpler and run from the command line.",
+    long_description=long_description,
+    long_description_content_type="text/markdown",
+    url="https://tildegit.org/cmccabe/linkulator2",
+    packages=find_packages(),
+    classifiers=[
+        "Programming Language :: Python :: 3",
+        "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
+        "Operating System :: POSIX",
+    ],
+    python_requires='>=3.6',
+)

tox.ini

@@ -0,0 +1,13 @@
+# tox (https://tox.readthedocs.io/) is a tool for running tests
+# in multiple virtualenvs. This configuration file will run the
+# test suite on all supported python versions. To use it, "pip install tox"
+# and then run "tox" from this directory.
+
+[tox]
+envlist = py36, py37, py38
+
+[testenv]
+deps = 
+
+commands =
+    python3 -m unittest discover -s tests -p "*_test.py"