Makes build/CI work with Python 3.9 (#152)

Updates CI configuration, tox configuration, requirements, and README.
Specifically adds more information around `tox`, upgrading
`pip`/`setuptools`, and using `venv` for this.  Also adds `tox` to the
requirements file to immediately make it available.

Also removes 2.7/3.4/3.5 as these are very much past end of life.
Updates `requirements.txt` to pick up updates for things like `pytest`
whose older versions don't work on 3.9.

Fixes a test `__str__` implementation to work in Python 3.9.

.travis.yml

@@ -1,16 +1,12 @@
 language: python
-dist: xenial
+dist: bionic
 matrix:
   include:
-    - python: "2.7"
-    - python: "3.4"
-    - python: "3.5"
     - python: "3.6"
     - python: "3.7"
-    - python: "pypy"
-    # https://github.com/travis-ci/travis-ci/issues/9542
-    # pypy3 < 6.0.0 fails due to discrepancies with decimal...
-    #- python: "pypy3"
+    - python: "3.8"
+    - python: "3.9"
+    - python: "pypy3"
 install:
   - "pip install --upgrade setuptools"
   - "pip install -r requirements.txt"

README.md

@@ -5,7 +5,7 @@ for Python.
 [![Build Status](https://travis-ci.org/amzn/ion-python.svg?branch=master)](https://travis-ci.org/amzn/ion-python)
 [![Documentation Status](https://readthedocs.org/projects/ion-python/badge/?version=latest)](https://ion-python.readthedocs.io/en/latest/?badge=latest)
 
-This package is designed to work with **Python 2.7+** and **Python 3.4+**
+This package is designed to work with **Python 3.6+**
 
 ## Getting Started
 
@@ -52,6 +52,8 @@ It is recommended to use `venv` to create a clean environment to build/test Ion
 $ python3 -m venv ./venv
 ...
 $ . venv/bin/activate
+$ pip install -U pip
+$ pip install -U setuptools
 $ pip install -r requirements.txt
 $ pip install -e .
 ```
@@ -66,16 +68,19 @@ $ python setup.py test
 In order to verify that all platforms we support work with Ion Python, we use a combination
 of [tox](http://tox.readthedocs.io/en/latest/) with [pyenv](https://github.com/yyuu/pyenv).
 
+We recommend that you use tox within a virtual environment to isolate from whatever is in the system
+installed Python (`requirements.txt` installs `tox`).
+
 Install relevant versions of Python:
 
 ```
-$ for V in 2.7.16 3.4.10 3.5.7 3.6.8 3.7.3 pypy2.7-7.1.1 pypy3.6-7.1.1; do pyenv install $V; done
+$ for V in 3.6.13 3.7.10 3.8.10 3.9.5 pypy3.7-7.3.5; do pyenv install $V; done
 ```
 
 Once you have these installations, add them as a local `pyenv` configuration
 
 ```
-$ pyenv local 2.7.16 3.4.10 3.5.7 3.6.8 3.7.3 pypy2.7-7.1.1 pypy3.6-7.1.1
+$ pyenv local 3.6.13 3.7.10 3.8.10 3.9.5 pypy3.7-7.3.5
 ```
 
 Assuming you have `pyenv` properly set up (making sure `pyenv init` is evaluated into your shell),
@@ -85,14 +90,14 @@ you can now run `tox`:
 # Run tox for all versions of python which executes py.test.
 $ tox
 
-# Run tox for just Python 2.7 and 3.5.
-$ tox -e py27,py35
+# Run tox for just Python 3.8 and 3.9.
+$ tox -e py38,py39
 
 # Run tox for a specific version and run py.test with high verbosity
-$ tox -e py27 -- py.test -vv
+$ tox -e py39 -- py.test -vv
 
 # Run tox for a specific version and just the virtual env REPL.
-$ tox -e py27 -- python
+$ tox -e py39 -- python
 ```
 
 ## TODO

requirements.txt

@@ -1,5 +1,16 @@
+appdirs==1.4.4
+attrs==21.2.0
+distlib==0.3.2
+filelock==3.0.12
+iniconfig==1.1.1
 jsonconversion==0.2.12
+packaging==20.9
+pluggy==0.13.1
 py==1.10.0
-pytest==2.9.2
-pytest-runner==2.8
-six==1.15.0
+pyparsing==2.4.7
+pytest==6.2.4
+pytest-runner==5.3.1
+six==1.16.0
+toml==0.10.2
+tox==3.23.1
+virtualenv==20.4.7

tests/test_core_multimap.py

@@ -6,7 +6,7 @@
 
 class _P(record('pairs', 'expected_all_values', 'expected_single_value', 'expected_total_len')):
     def __str__(self):
-        return self.desc
+        return '{name}'.format(name=self.pairs)
 
 
 ALL_DATA = _P(

tox.ini

@@ -1,6 +1,8 @@
 [tox]
-envlist = py27,py34,py35,py36,py37,pypy2,pypy3
+envlist = py36,py37,py38,py39,pypy3
 
 [testenv]
+requires= pip >= 21.1.2
+  setuptools >= 57.0.0
 deps=-rrequirements.txt
 commands={posargs:py.test}