Travis help: explicitely require cov-core==1.15.0

so to shutdown annoying prob during coverage :

test_port_not_free (test_bad_start.Test_Scheduler_Bad_Start) ... ok
Coverage.py warning: No data was collected.
Traceback (most recent call last):
  File "/opt/python/2.6.9/lib/python2.6/multiprocessing/util.py", line 235, in _run_finalizers
    finalizer()
  File "/opt/python/2.6.9/lib/python2.6/multiprocessing/util.py", line 174, in __call__
    res = self._callback(*self._args, **self._kwargs)
  File "/home/travis/virtualenv/python2.6.9/lib/python2.6/site-packages/cov_core.py", line 20, in multiprocessing_finish
    cov.save()
  File "/home/travis/virtualenv/python2.6.9/lib/python2.6/site-packages/coverage/control.py", line 493, in save
    self.data.write(suffix=data_suffix)
  File "/home/travis/virtualenv/python2.6.9/lib/python2.6/site-packages/coverage/data.py", line 91, in write
    self.write_file(filename)
  File "/home/travis/virtualenv/python2.6.9/lib/python2.6/site-packages/coverage/data.py", line 131, in write_file
    fdata = open(filename, 'wb')
IOError: [Errno 2] No such file or directory: '/tmp/tmpOumlg1/.coverage.testing-worker-linux-027f0490-2-7771-linux-4-50667445.3028.493619'

.travis.yml

@@ -12,7 +12,7 @@ install:
 # so we must combine them in the end
 script:
   - cd test
-  - nosetests -xv --process-restartworker --processes=1 --process-timeout=999999999  --with-cov --cov=alignak
+  - nosetests -xv --process-restartworker --processes=1 --process-timeout=999999999  --with-coverage --cover-package=alignak
   - coverage combine
   - cd .. && pep8 --max-line-length=100 --ignore=E303,E302,E301,E241 --exclude='*.pyc' alignak/*
 # specific call to launch coverage data into coveralls.io

test/requirements.txt

@@ -5,6 +5,7 @@ mock
 coveralls==0.5
 nose-cov==1.6
 coverage==3.7.1
-nose==1.3.4
+nose==1.3.6
 pylint==1.4.1
 pep8==1.5.7
+cov-core==1.15.0

test/setup_test.sh

@@ -27,3 +27,6 @@ cd $BASE_PATH
 # install prog AND tests requirements :
 pip install -r test/requirements.txt
 python setup.py develop
+
+# for eventual debug help to know what libs versions we have:
+pip freeze