[coverage] Add coverage with coveralls 👖

There are other services to get the code coverage, this commit implements it with `coveralls` because is the one that uses the main project `kivy`

Also:
  - add coverage badge to README.md file
  - add file `.coveragerc` to configure the behaviour of our coverage

Author: opacam

.coveragerc

@@ -0,0 +1,10 @@
+[run]
+omit =
+    *test*
+
+[report]
+exclude_lines =
+    pragma: no cover
+    def __repr__
+    raise NotImplementedError
+    if __name__ == .__main__.:

.travis.yml

@@ -9,9 +9,11 @@ services:
 
 before_install:
   - travis_retry sudo apt update -qq
-  - travis_retry sudo apt install -qq --no-install-recommends python2.7 python3 python3-venv python3-virtualenv
+  # to successfully send the coveralls reports we need pyOpenSSL
+  - travis_retry sudo apt install -qq --no-install-recommends python2.7 python3 python3-venv python3-virtualenv python3-setuptools python3-pip python3-openssl
   # (venv/virtualenv are both used by tests/test_pythonpackage.py)
   - sudo pip install tox>=2.0
+  - sudo pip3 install coveralls
   # https://github.com/travis-ci/travis-ci/issues/6069#issuecomment-266546552
   - git remote set-branches --add origin master
   - git fetch
@@ -39,6 +41,8 @@ script:
   # case that the travis log doesn't produce any output for more than 10 minutes
   - while sleep 540; do echo "==== Still running (travis, don't kill me) ===="; done &
   - docker build --tag=p4a --file Dockerfile.py3 .
-  - docker run -e CI p4a /bin/sh -c "$COMMAND"
+  - docker run -e CI -e TRAVIS_JOB_ID="$TRAVIS_JOB_ID" -e TRAVIS_BRANCH="$TRAVIS_BRANCH" p4a /bin/sh -c "$COMMAND"
   # kill the background process started before run docker
   - kill %1
+after_success:
+  - coveralls

README.md

@@ -2,6 +2,7 @@ python-for-android
 ==================
 
 [![Build Status](https://travis-ci.org/kivy/python-for-android.svg?branch=master)](https://travis-ci.org/kivy/python-for-android)
+[![Coverage Status](https://coveralls.io/repos/github/kivy/python-for-android/badge.svg?branch=master&kill_cache=1)](https://coveralls.io/github/kivy/python-for-android?branch=master)
 [![Backers on Open Collective](https://opencollective.com/kivy/backers/badge.svg)](#backers) 
 [![Sponsors on Open Collective](https://opencollective.com/kivy/sponsors/badge.svg)](#sponsors) 
 

tox.ini

@@ -7,12 +7,20 @@ deps =
     mock
     pytest
     virtualenv
+    py3: coveralls
 # makes it possible to override pytest args, e.g.
 # tox -- tests/test_graph.py
 commands = pytest {posargs:tests/}
+passenv = TRAVIS TRAVIS_*
 setenv =
     PYTHONPATH={toxinidir}
 
+[testenv:py3]
+# for py3 env we will get code coverage
+commands =
+    coverage run --branch --source=pythonforandroid -m pytest {posargs:tests/}
+    coverage report -m
+
 [testenv:pep8]
 deps = flake8
 commands = flake8 pythonforandroid/ tests/ ci/