Add workaround for Travis CI environment issue.

Per https://github.com/travis-ci/travis-ci/issues/5363

.travis.yml

@@ -11,6 +11,7 @@ install:
   - chmod +x /tmp/urchin/package/urchin
   - '[ -z "$WITHOUT_CURL" ] || sudo apt-get remove curl -y'
 script:
+  - export PATH=$(echo $PATH | sed 's/::/:/')
   - NVM_DIR=$TRAVIS_BUILD_DIR make TEST_SUITE=$TEST_SUITE URCHIN=/tmp/urchin/package/urchin test-$SHELL
 env:
   - SHELL=bash TEST_SUITE=install_script