CI: Drop defunct rackspace wheelhouse

Author: effigies

.travis.yml

@@ -16,10 +16,8 @@ env:
         - DEPENDS="numpy scipy matplotlib h5py pillow pydicom indexed_gzip"
         - INSTALL_TYPE="setup"
         - CHECK_TYPE="test"
-        - EXTRA_WHEELS="https://3f23b170c54c2533c070-1c8a9b3114517dc5fe17b7c3f8c63a43.ssl.cf2.rackcdn.com"
         - NIGHTLY_WHEELS="https://pypi.anaconda.org/scipy-wheels-nightly/simple"
-        - EXTRA_PIP_FLAGS="--find-links=$EXTRA_WHEELS"
-        - PRE_PIP_FLAGS="--pre $EXTRA_PIP_FLAGS --extra-index-url $NIGHTLY_WHEELS"
+        - PRE_PIP_FLAGS="--pre --extra-index-url $NIGHTLY_WHEELS"
 
 python:
     - 3.7