Ignore python2 Django2 combination

Author: Martin Pauly

.travis.yml

@@ -69,6 +69,8 @@ matrix:
         - python: 'pypy'
         - python: 2.7
           env: DJANGO_VERSION=">=2.0,<2.1" VERSION_ES=">=2.0.0,<3.0.0"
+        - python: 2.7
+          env: DJANGO_VERSION=">=2.0,<2.1" VERSION_ES=">=1.0.0,<2.0.0"
 
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