Note on the new wheel bug we're hitting [skip ci]

.travis.yml

@@ -14,13 +14,16 @@ install:
     # First install a newer pip so that it can use the wheel cache
     # (only needed until travis upgrades pip to 7.x; note that the 3.5
     # environment uses pip 7.1 by default)
-    - travis_retry pip install -U pip wheel
-    # Then start installing our deps. Note that use of --build-options / --global-options / --install-options
+    - travis_retry pip install -U pip
+    # Then start installing our deps so they can be cached. Note that use of --build-options / --global-options / --install-options
     # disables the cache.
     # Bug https://bitbucket.org/pypa/wheel/issues/146/wheel-building-fails-on-cpython-350b3
     # means that installing cython on cpython 3.5 cannot use the wheel cache, which
     # means that the LINT=true case is quite slow (2.5 minutes). If this takes very long to fix,
-    # we might want to do some refactoring to move installation into the makefile or a script.
+    # we might want to do some refactoring to move installation into the makefile or a script (so the LINT=true case
+    # isn't slowed down).
+    # That was fixed in wheel 0.25, but now we're hitting https://bitbucket.org/pypa/wheel/issues/148/unorderable-types-error-for-python-3
+    - travis_retry pip install -U wheel
     - travis_retry pip install -U tox cython greenlet pep8 pyflakes "coverage>=4.0b3" "coveralls>=1.0b1"
 script:
     - if [[ $TRAVIS_PYTHON_VERSION == '2.7' && $LINT == true ]]; then python setup.py develop && make travis_test_linters; elif [[ $LINT == false && $TRAVIS_PYTHON_VERSION == 'pypy' ]]; then python setup.py develop && make fulltoxtest; elif [[ $LINT == false ]]; then python setup.py develop && make fulltoxtest; fi