Fixes #868 -- test on py38 (#870)

diff --git a/.travis.yml b/.travis.yml
index 5c83f88..b58d7cb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -29,6 +29,8 @@
     env: TOXENV=py36
   - python: "3.7"
     env: TOXENV=py37
+  - python: "3.8"
+    env: TOXENV=py38
   - python: "pypy2.7-5.10.0"
     env: TOXENV=pypy
   - python: "pypy3.5-5.10.1"
@@ -45,6 +47,8 @@
     env: TOXENV=py36-cryptographyMaster
   - python: "3.7"
     env: TOXENV=py37-cryptographyMaster
+  - python: "3.8"
+    env: TOXENV=py38-cryptographyMaster
   - python: "pypy2.7-5.10.0"
     env: TOXENV=pypy-cryptographyMaster
   - python: "pypy3.5-5.10.1"
@@ -61,6 +65,8 @@
     env: TOXENV=py36-cryptographyMinimum
   - python: "3.7"
     env: TOXENV=py37-cryptographyMinimum
+  - python: "3.8"
+    env: TOXENV=py38-cryptographyMinimum
   - python: "pypy2.7-5.10.0"
     env: TOXENV=pypy-cryptographyMinimum
   - python: "pypy3.5-5.10.1"
@@ -100,6 +106,7 @@
   - env: TOXENV=py35-cryptographyMaster
   - env: TOXENV=py36-cryptographyMaster
   - env: TOXENV=py37-cryptographyMaster
+  - env: TOXENV=py38-cryptographyMaster
   - env: TOXENV=pypy-cryptographyMaster
   - env: TOXENV=pypy3-cryptographyMaster
 
diff --git a/setup.py b/setup.py
index ec66539..f6d5499 100755
--- a/setup.py
+++ b/setup.py
@@ -81,6 +81,7 @@
             'Programming Language :: Python :: 3.5',
             'Programming Language :: Python :: 3.6',
             'Programming Language :: Python :: 3.7',
+            'Programming Language :: Python :: 3.8',
 
             'Programming Language :: Python :: Implementation :: CPython',
             'Programming Language :: Python :: Implementation :: PyPy',
diff --git a/tox.ini b/tox.ini
index faecfbf..58cfd7a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = {pypy,pypy3,py27,py34,py35,py36,py37}{,-cryptographyMaster,-cryptographyMinimum}{,-randomorder},py27-twistedMaster,pypi-readme,check-manifest,flake8,docs,coverage-report
+envlist = {pypy,pypy3,py27,py34,py35,py36,py37,py38}{,-cryptographyMaster,-cryptographyMinimum}{,-randomorder},py27-twistedMaster,pypi-readme,check-manifest,flake8,docs,coverage-report
 
 [testenv]
 whitelist_externals =