Fix run_unit_tests.sh

[afarbos]

I don't know if it's a mistake, but the airflow/www/static/coverage does not exist. So, if anyone want to try run_unit_tests.sh, he will have an error from rm and he will not able to use it.

Moreover, in https://github.com/airbnb/airflow/blob/master/CONTRIBUTING.md#testing you don't specify to install nose so you can add it to your requierements.txt or specify it in your CONTRIBUTING.md

To finish, are you interested by the output of the test ?

[mistercrunch]

Yes indeed we are interested in the html results of the test. Notice that there's a symlink pointing to that folder from the web server's static folder here:
https://github.com/airbnb/airflow/blob/master/airflow/www/static/docs

You're right, nose should be in the requirements.txt and the setup.py devel extras_require

The idea with the rm statement is to make room for the new export, the bash script should create the folder if it doesn't exist, then empty it to make place for the output of nose

[artwr]

@globus. I had an old open PR to do this :

if [[ -d "airflow/www/static/coverage" ]]
then
  rm airflow/www/static/coverage/*
else
  mkdir -p "airflow/www/static/coverage"
fi

Feel free to reuse

[afarbos]

Your else is not usefull because you use -p for mkdir and just adding -f to remove should the error message and so you can remove the if.

[mistercrunch]

a6f42ab and 49201ee are equivalent to this, closing. Thanks for pointing these out!