Add a test that setuptools can be installed in a clean environment

.travis.yml

@@ -27,6 +27,9 @@ script:
  #- python -m tox
  - tox
 
+ # Check that setuptools can be installed in a clean environment
+ - ./clean_install.sh
+
 deploy:
   provider: pypi
   # Also update server in setup.cfg

clean_install.sh

+#!/usr/bin/env bash
+
+set -o errexit
+set -o xtrace
+
+# Create a temporary directory to install the virtualenv in
+VENV_DIR="$(mktemp -d)"
+function cleanup { rm -rf "$VENV_DIR" }
+trap cleanup EXIT
+
+# Create a virtualenv that doesn't have pip or setuptools installed
+wget https://raw.githubusercontent.com/pypa/virtualenv/master/virtualenv.py
+python virtualenv.py --no-wheel --no-pip --no-setuptools "$VENV_DIR"
+source "$VENV_DIR/bin/activate"
+
+# Now try to install setuptools
+python bootstrap.py
+python setup.py install