Remove python 3.5 support; add python 3.8 support

- Python 3.5 has reached end-of-life.
- Add support for Python 3.8
- Move dist to bionic (xenial is EOL in April)
- Upgrade pip in travis.yml's `before_install`. this should install a wheel
  for pyca/cryptography
- Install rust for pypy builds. It is a requirement for cryptography as no
  pypy wheels exist.

1 files changed, 4 insertions, 4 deletions

diff --git a/tox.ini b/tox.ini
index aad4538..deb7cc7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py35,py36,py37,pypy,pypy3,docs,readme,bandit,isort
+envlist = py36,py37,py38,pypy,pypy3,docs,readme,bandit,isort
 
 [testenv]
 deps=
@@ -22,21 +22,21 @@ commands=make clean html
 
 # tox -e readme to mimick PyPI long_description check
 [testenv:readme]
-basepython=python3.7
+basepython=python3.8
 deps=twine>=1.12.0
 whitelist_externals=echo
 commands=
         twine check dist/*
 
 [testenv:bandit]
-basepython=python3.7
+basepython=python3.8
 skipsdist=True
 deps=bandit
 commands=bandit -b bandit.json -r oauthlib/
 whitelist_externals=bandit
 
 [testenv:isort]
-basepython = python3.7
+basepython = python3.8
 usedevelop = false
 deps = isort
 changedir = {toxinidir}