try

.travis.yml

@@ -4,6 +4,7 @@ python:
 - '2.7'
 - '3.5'
 - '3.6'
+- 'pypy3'
 env:
   global:
   - LD_LIBRARY_PATH=./libsecp256k1_ext/.libs
@@ -55,6 +56,11 @@ addons:
     - libffi-dev
     - libgmp-dev
 before_install:
+- cd $HOME
+- mkdir bin
+- export PATH=$HOME/bin:$PATH
+- "if [[ $TRAVIS_PYTHON_VERSION == 'pypy3' ]]; then deactivate && wget https://bitbucket.org/squeaky/portable-pypy/downloads/pypy3.5-5.7.1-beta-linux_x86_64-portable.tar.bz2 && tar -jxf pypy3.5-5.7.1-beta-linux_x86_64-portable.tar.bz2 && echo 'Setting up aliases...' && export PATH=$HOME/pypy3.5-5.7.1-beta-linux_x86_64-portable/bin/:$PATH && ln -s ~/pypy3.5-5.7.1-beta-linux_x86_64-portable/bin/pypy3.5 ~/bin/python && echo 'Setting up pip...' && pypy3.5-5.7.1-beta-linux_x86_64-portable/bin/pypy -m ensurepip && ln -s ~/pypy3.5-5.7.1-beta-linux_x86_64-portable/bin/pip3.5 ~/bin/pip ; fi"
+- cd $TRAVIS_BUILD_DIR
 - chmod +x .travis/prepare_windows_build.sh .travis/build_windows_wheels.sh
 - .travis/prepare_windows_build.sh
 - source .travis/install.sh

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 mintoxversion = 2.0
-envlist = py{27,35,36,py}-{default,experimental}
+envlist = py{27,35,36,py3}-{default,experimental}
 
 [testenv]
 passenv = *