Correct typo

Author: kroenlein

.travis.yml

@@ -10,7 +10,7 @@ env:
   - UPGRADES="pint --upgrade pandas --upgrade"
   - UPGRADES=""
 install:
-  - pip install --only-binary ':all:' -r requirements.txt -r test_requirements.txt -e . UPGRADES
+  - pip install --only-binary ':all:' -r requirements.txt -r test_requirements.txt -e . $UPGRADES
 script:
 - bash scripts/run_tests.sh
 - cd docs; make html; cd ..;