use an if statement instead of a && because the && was resulting in a failing exit code

Author: radix

.travis.yml

@@ -11,10 +11,10 @@ install:
     - pip install -r dev-requirements.txt
     - pip install sphinx sphinx_rtd_theme
     # black isn't installing on pypy3, so just skip it
-    - '[ "$TRAVIS_PYTHON_VERSION" != "pypy3" ] && pip install black'
+    - 'if [ "$TRAVIS_PYTHON_VERSION" != "pypy3" ]; then pip install black; fi'
 script:
     - flake8
-    - '[ "$TRAVIS_PYTHON_VERSION" != "pypy3" ] && black --check .'
+    - 'if [ "$TRAVIS_PYTHON_VERSION" != "pypy3" ]; then black --check .; fi'
     - pytest
     - make doc