Fix cov-report tox environment run

[insspb]

• Cookiecutter version: master

(cookiecutter27) insspb@insspb-notebook:~/git/cookiecutter$ tox -e cov-report
cov-report create: /home/insspb/git/cookiecutter/.tox/cov-report
cov-report installdeps: -rtest_requirements.txt
cov-report installed: DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support,atomicwrites==1.3.0,attrs==19.3.0,configparser==4.0.2,contextlib2==0.6.0.post1,cookiecutter==1.7.0,coverage==5.1,freezegun==0.3.15,funcsigs==1.0.2,importlib-metadata==1.6.0,mock==3.0.5,more-itertools==5.0.0,packaging==20.3,pathlib2==2.3.5,pluggy==0.13.1,py==1.8.1,pyparsing==2.4.7,pytest==4.6.9,pytest-cov==2.8.1,pytest-mock==2.0.0,python-dateutil==2.8.1,scandir==1.10.0,six==1.14.0,wcwidth==0.1.9,zipp==1.2.0
cov-report run-test-pre: PYTHONHASHSEED='3635409391'
cov-report run-test: commands[0] | pytest --cov=cookiecutter --cov-report=term --cov-report=html
ImportError while loading conftest '/home/insspb/git/cookiecutter/tests/conftest.py'.
tests/conftest.py:11: in <module>
    from cookiecutter import utils
cookiecutter/utils.py:14: in <module>
    from cookiecutter.prompt import read_user_yes_no
cookiecutter/prompt.py:8: in <module>
    import click
E   ImportError: No module named click
ERROR: InvocationError for command /home/insspb/git/cookiecutter/.tox/cov-report/bin/pytest --cov=cookiecutter --cov-report=term --cov-report=html (exited with code 4)
___________________________________________________________________________________________________________ summary ___________________________________________________________________________________________________________
ERROR:   cov-report: commands failed