Remove extra function call from context manger API

[ionelmc]

As mentioned in #9 (comment)

So I still use python 2.7 🙄

PS. How come you're not using pytest-cov?

[okken]

Thanks Ionel.

[okken]

With coverage running pytest

(pytest-check) $ coverage erase
(pytest-check) $ coverage run --source=src -m pytest
=================== test session starts ===================
platform darwin -- Python 3.7.0, pytest-4.2.0, py-1.7.0, pluggy-0.8.1
rootdir: /Users/okken/projects/pytest-check, inifile:
plugins: cov-2.6.1, check-0.3.4
collected 27 items                                        

tests/test_check.py .....................           [ 77%]
tests/test_check_context_manager.py ...             [ 88%]
tests/test_check_fixture.py .                       [ 92%]
tests/test_check_func_decorator.py ..               [100%]

================ 27 passed in 1.21 seconds ================
(pytest-check) $ coverage report
Name                                Stmts   Miss  Cover
-------------------------------------------------------
src/pytest_check/__init__.py            3      0   100%
src/pytest_check/check_methods.py     101      0   100%
src/pytest_check/plugin.py             22      0   100%
-------------------------------------------------------
TOTAL                                 126      0   100%

[okken]

I usually use pytest-cov for non-plugin work and straight coverage for plugin work.
I am at 100% test coverage now with launching pytest from coverage.
But with pytest-cov, I only get 55% coverage.

(pytest-check) $ pytest --cov=src
=================== test session starts ===================
platform darwin -- Python 3.7.0, pytest-4.2.0, py-1.7.0, pluggy-0.8.1
rootdir: /Users/okken/projects/pytest-check, inifile:
plugins: cov-2.6.1, check-0.3.4
collected 27 items                                        

tests/test_check.py .....................           [ 77%]
tests/test_check_context_manager.py ...             [ 88%]
tests/test_check_fixture.py .                       [ 92%]
tests/test_check_func_decorator.py ..               [100%]

---------- coverage: platform darwin, python 3.7.0-final-0 -----------
Name                                Stmts   Miss  Cover
-------------------------------------------------------
src/pytest_check/__init__.py            3      3     0%
src/pytest_check/check_methods.py     101     49    51%
src/pytest_check/plugin.py             22      5    77%
-------------------------------------------------------
TOTAL                                 126     57    55%


================ 27 passed in 1.37 seconds ================