fix tests

.travis.yml

@@ -66,6 +66,7 @@ install:
     - |
       if [[ $TRAVIS_OS_NAME == 'osx' ]]; then
           if [[ -n "$BREW_PYTHON_PACKAGE" ]]; then
+              export HOMEBREW_NO_INSTALL_CLEANUP=1
               brew update
               if ! brew list --versions "$BREW_PYTHON_PACKAGE" >/dev/null; then
                   brew install "$BREW_PYTHON_PACKAGE"

requirements-dev.txt

@@ -6,5 +6,4 @@ pytest-httpbin>=0.0.6
 docutils
 wheel
 pycodestyle
-pyOpenSSL
-twine
+twine

setup.py

@@ -7,6 +7,7 @@ from setuptools import setup, find_packages
 from setuptools.command.test import test as TestCommand
 
 import httpie
+from httpie.compat import is_py27
 
 
 class PyTest(TestCommand):
@@ -33,6 +34,9 @@ tests_require = [
     'mock',
 ]
 
+if is_py27:
+    tests_require.append('pyOpenSSL')
+
 
 install_requires = [
     'requests>=2.21.0',