fix for python2.6 and pip 1.5

.travis.yml

@@ -2,5 +2,5 @@ language: python
 python:
   - "2.6"
   - "2.7"
-install: "pip install -r requirements.txt --use-mirrors"
+install: "pip install -r requirements.txt"
 script: "fab travis_ci"

requirements.txt

@@ -10,6 +10,3 @@ mock==1.0.1
 # Requirements for OpenSlides handbook/documentation in alphabetical order
 Sphinx==1.2b3
 sphinx-bootstrap-theme==0.2.4
-
-# For Python 2.6 support
-argparse==1.2.1

requirements_production.txt

@@ -10,3 +10,7 @@ reportlab>=2.7,<2.8
 sockjs-tornado>=1.0,<1.1
 tornado>=3.1,<3.2
 whoosh>=2.5,<2.6
+
+# For Python 2.6 support
+--allow-external argparse
+argparse==1.2.1