pytest error

(coala) akhelesh@Hubble:/media/Vol-B/Projects/coala-bears$ pytest ./tests/python/PyLintBearTest.py
Traceback (most recent call last):
  File "/usr/local/bin/pytest", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.6/dist-packages/_pytest/config/__init__.py", line 55, in main
    config = _prepareconfig(args, plugins)
  File "/usr/local/lib/python3.6/dist-packages/_pytest/config/__init__.py", line 180, in _prepareconfig
    pluginmanager=pluginmanager, args=args
  File "/usr/local/lib/python3.6/dist-packages/pluggy/hooks.py", line 258, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/usr/local/lib/python3.6/dist-packages/pluggy/manager.py", line 67, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/local/lib/python3.6/dist-packages/pluggy/manager.py", line 61, in <lambda>
    firstresult=hook.spec_opts.get('firstresult'),
  File "/usr/local/lib/python3.6/dist-packages/pluggy/callers.py", line 196, in _multicall
    gen.send(outcome)
  File "/usr/local/lib/python3.6/dist-packages/_pytest/helpconfig.py", line 89, in pytest_cmdline_parse
    config = outcome.get_result()
  File "/usr/local/lib/python3.6/dist-packages/pluggy/callers.py", line 76, in get_result
    raise ex[1].with_traceback(ex[2])
  File "/usr/local/lib/python3.6/dist-packages/pluggy/callers.py", line 180, in _multicall
    res = hook_impl.function(*args)
  File "/usr/local/lib/python3.6/dist-packages/_pytest/config/__init__.py", line 612, in pytest_cmdline_parse
    self.parse(args)
  File "/usr/local/lib/python3.6/dist-packages/_pytest/config/__init__.py", line 777, in parse
    self._preparse(args, addopts=addopts)
  File "/usr/local/lib/python3.6/dist-packages/_pytest/config/__init__.py", line 739, in _preparse
    early_config=self, args=args, parser=self._parser
  File "/usr/local/lib/python3.6/dist-packages/pluggy/hooks.py", line 258, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/usr/local/lib/python3.6/dist-packages/pluggy/manager.py", line 67, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/local/lib/python3.6/dist-packages/pluggy/manager.py", line 61, in <lambda>
    firstresult=hook.spec_opts.get('firstresult'),
  File "/usr/local/lib/python3.6/dist-packages/pluggy/callers.py", line 201, in _multicall
    return outcome.get_result()
  File "/usr/local/lib/python3.6/dist-packages/pluggy/callers.py", line 76, in get_result
    raise ex[1].with_traceback(ex[2])
  File "/usr/local/lib/python3.6/dist-packages/pluggy/callers.py", line 180, in _multicall
    res = hook_impl.function(*args)
  File "/home/akhelesh/.local/lib/python3.6/site-packages/pytest_cov/plugin.py", line 98, in pytest_load_initial_conftests
    plugin = CovPlugin(early_config.known_args_namespace, early_config.pluginmanager)
  File "/home/akhelesh/.local/lib/python3.6/site-packages/pytest_cov/plugin.py", line 145, in __init__
    self.start(engine.Central)
  File "/home/akhelesh/.local/lib/python3.6/site-packages/pytest_cov/plugin.py", line 167, in start
    self.cov_controller.start()
  File "/home/akhelesh/.local/lib/python3.6/site-packages/pytest_cov/engine.py", line 159, in start
    self.cov.erase()
  File "/home/akhelesh/.local/lib/python3.6/site-packages/coverage/control.py", line 717, in erase
    self._init()
  File "/home/akhelesh/.local/lib/python3.6/site-packages/coverage/control.py", line 219, in _init
    self.plugins = Plugins.load_plugins(self.config.plugins, self.config, self.debug)
  File "/home/akhelesh/.local/lib/python3.6/site-packages/coverage/plugin_support.py", line 39, in load_plugins
    __import__(module)
  File "/home/akhelesh/.local/lib/python3.6/site-packages/coverage_env_plugin.py", line 4, in <module>
    from packaging.markers import default_environment
ModuleNotFoundError: No module named 'packaging'

(coala) akhelesh@Hubble:/media/Vol-B/Projects/coala-bears$ pip freeze
aenum==2.0.10
ansicolor==0.2.6
apertium-lint==0.29
apipkg==1.5
appdirs==1.4.3
args==0.1.0
astroid==2.1.0
atomicwrites==1.2.1
attrs==18.2.0
autoflake==0.7
autopep8==1.4.3
Babel==2.6.0
backcall==0.1.0
bandit==1.5.1
bashate==0.5.1
bitstring==3.1.5
brotlipy==0.7.0
cached-property==1.4.3
certifi==2018.11.29
cffi==1.11.5
chardet==3.0.4
cli-helpers==1.0.2
Click==7.0
clint==0.5.1
cmakelint==1.3.4.1
coala==0.12.0.dev99999999999999
-e git+https://github.com/Akhelesh/coala-bears.git@7c5e4c83469ba00ca2494c4c86adb2f53bf96816#egg=coala_bears
-e git+https://gitlab.com/coala/coala-utils.git@f92226c326f044400908308b76a4e0fbb38447a2#egg=coala_utils
codecov==2.0.15
colorama==0.3.9
colorlog==2.10.0
coverage==4.4.1
coverage-config-reload-plugin==0.2.0
coverage-env-plugin==0.1
cppclean==0.12
cpplint==1.3.0
crayons==0.1.2
decorator==4.3.0
defusedxml==0.5.0
dennis==0.9
-e git+https://gitlab.com/coala/package_manager.git@ecc7520fd045936aff13c074a2a01565dde7471e#egg=dependency_management
docopt==0.6.2
docutils==0.14
docutils-ast-writer==0.1.2
dominate==2.3.5
dparse==0.4.1
eradicate==0.1.6
execnet==1.5.0
future==0.17.1
git-url-parse==1.1.0
gitdb2==2.0.5
GitPython==2.1.11
gprof2dot==2017.9.19
guess-language-spirit==0.5.3
html-linter==0.4.0
HTTPolice==0.5.2
idna==2.8
ipdb==0.11
ipython==7.2.0
ipython-genutils==0.2.0
isort==4.3.4
jedi==0.13.2
Jinja2==2.10
jsonschema==3.0.0a3
jupyter-core==4.4.0
language-check==1.1
lazy-object-proxy==1.3.1
libclang-py3==3.4.0
lml==0.0.7
mando==0.3.3
MarkupSafe==1.1.0
mccabe==0.6.1
memento-client==0.6.1
moban==0.3.5
more-itertools==4.3.0
munkres3==1.0.5.5
mypy==0.590
nbformat==4.4.0
nltk==3.4
packaging==16.8
parso==0.3.1
pathspec==0.5.9
pbr==5.1.1
pexpect==4.6.0
pickleshare==0.7.5
pip-api==0.0.4
pkginfo==1.4.2
pluggy==0.7.1
polib==1.1.0
prompt-toolkit==2.0.7
proselint==0.7.0
ptyprocess==0.6.0
py==1.7.0
pycodestyle==2.4.0
pycparser==2.19
pydocstyle==2.1.1
pyflakes==2.0.0
Pygments==2.3.0
pylint==2.2.2
pyparsing==2.3.0
PyPrint==0.2.6
pyroma==2.2
pyrsistent==0.14.7
pytest==3.6.4
pytest-cov==2.6.0
pytest-env==0.6.2
pytest-forked==0.2
pytest-instafail==0.3.0
pytest-mock==1.10.0
pytest-profiling==1.3.0
pytest-pythonpath==0.7.3
pytest-reorder==0.1.1
pytest-reqs==0.2.0
pytest-timeout==1.3.3
pytest-travis-fold==1.3.0
pytest-xdist==1.25.0
pytz==2018.7
PyYAML==3.13
radon==1.4.0
requests==2.21.0
requests-mock==1.5.2
requests-toolbelt==0.8.0
restructuredtext-lint==1.0.1
rstcheck==3.3.1
ruamel.yaml==0.15.81
safety==1.8.4
sarge==0.1.5.post0
scspell3k==2.1
singledispatch==3.4.0.3
six==1.12.0
smmap2==2.0.5
snowballstemmer==1.2.1
sqlparse==0.2.4
stevedore==1.30.0
tabulate==0.8.2
template-remover==0.1.9
termcolor==1.1.0
terminaltables==3.1.0
testfixtures==5.3.1
traitlets==4.3.2
twine==1.7.4
typed-ast==1.1.0
unidiff==0.5.5
urllib3==1.24.1
vim-vint==0.3.18
vulture==0.25
wcwidth==0.1.7
wrapt==1.10.11
yamllint==1.12.1
yapf==0.21.0