Simplify install-on-travis.sh by adding requirements-travis.txt

Author: xolox

requirements-checks.txt

@@ -1,4 +1,4 @@
-# Python packages required to run `make check'.
+# Python packages required to run code style checks.
 flake8 >= 2.6.0
 flake8-docstrings >= 0.2.8
 pyflakes >= 1.2.3

requirements-tests.txt

@@ -1,3 +1,4 @@
+# Python packages required to run the test suite.
 mock >= 1.0.1
 pytest >= 2.6.1
 pytest-cov >= 2.2.1

requirements-travis.txt

@@ -0,0 +1,5 @@
+# Python packages required on Travis CI.
+--requirement=requirements-checks.txt
+--requirement=requirements-tests.txt
+--requirement=requirements.txt
+coveralls

scripts/install-on-travis.sh

@@ -2,10 +2,7 @@
 
 # Install the required Python packages.
 pip install pip-accel
-pip-accel install coveralls
-pip-accel install --requirement=requirements.txt
-pip-accel install --requirement=requirements-checks.txt
-pip-accel install --requirement=requirements-tests.txt
+pip-accel install --requirement=requirements-travis.txt
 
 # Install the project itself, making sure that potential character encoding
 # and/or decoding errors in the setup script are caught as soon as possible.