py.test error

err.sh

$ py.test --version

This is pytest version 2.6.3, imported from /usr/lib/python2.7/dist-packages/pytest.pyc
snim2:2073(0):pydgin$ pip install --user -r requirements.txt 
Downloading/unpacking pytest-cov (from -r requirements.txt (line 1))
  Downloading pytest-cov-1.8.1.tar.gz
  Running setup.py (path:/tmp/pip-build-ND85Ym/pytest-cov/setup.py) egg_info for package pytest-cov
    
Downloading/unpacking pytest-xdist (from -r requirements.txt (line 2))
  Downloading pytest-xdist-1.12.tar.gz
  Running setup.py (path:/tmp/pip-build-ND85Ym/pytest-xdist/setup.py) egg_info for package pytest-xdist
    
    no previously-included directories found matching '.hg'
Downloading/unpacking py>=1.4.22 (from pytest-cov->-r requirements.txt (line 1))
  Downloading py-1.4.28-py2.py3-none-any.whl (81kB): 81kB downloaded
Downloading/unpacking pytest>=2.6.0 (from pytest-cov->-r requirements.txt (line 1))
  Downloading pytest-2.7.1-py2.py3-none-any.whl (126kB): 126kB downloaded
Downloading/unpacking coverage<4.0a1,>=3.7.1 (from pytest-cov->-r requirements.txt (line 1))
  Downloading coverage-3.7.1.tar.gz (284kB): 284kB downloaded
  Running setup.py (path:/tmp/pip-build-ND85Ym/coverage/setup.py) egg_info for package coverage
    
    warning: no previously-included files matching '*.pyc' found anywhere in distribution
Downloading/unpacking cov-core>=1.14.0 (from pytest-cov->-r requirements.txt (line 1))
  Downloading cov-core-1.15.0.tar.gz
  Running setup.py (path:/tmp/pip-build-ND85Ym/cov-core/setup.py) egg_info for package cov-core
    
Downloading/unpacking execnet>=1.1 (from pytest-xdist->-r requirements.txt (line 2))
  Downloading execnet-1.3.0-py2.py3-none-any.whl
Installing collected packages: pytest-cov, pytest-xdist, py, pytest, coverage, cov-core, execnet
  Running setup.py install for pytest-cov
    
  Running setup.py install for pytest-xdist
    
    no previously-included directories found matching '.hg'
  Running setup.py install for coverage
    building 'coverage.tracer' extension
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/include/python2.7 -c coverage/tracer.c -o build/temp.linux-x86_64-2.7/coverage/tracer.o
    x86_64-linux-gnu-gcc -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-Bsymbolic-functions -Wl,-z,relro -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -Wl,-Bsymbolic-functions -Wl,-z,relro -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security build/temp.linux-x86_64-2.7/coverage/tracer.o -o build/lib.linux-x86_64-2.7/coverage/tracer.so
    
    warning: no previously-included files matching '*.pyc' found anywhere in distribution
    Installing coverage2 script to /home/snim2/.local/bin
    Installing coverage-2.7 script to /home/snim2/.local/bin
    Installing coverage script to /home/snim2/.local/bin
  Running setup.py install for cov-core
    
    
    Wrote pth file for subprocess measurement to /home/snim2/.local/lib/python2.7/site-packages/init_cov_core.pth
Successfully installed pytest-cov pytest-xdist py pytest coverage cov-core execnet
Cleaning up...

$ py.test --version
Traceback (most recent call last):
  File "/usr/bin/py.test", line 5, in <module>
    sys.exit(load_entry_point('pytest==2.6.3', 'console_scripts', 'py.test')())
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 521, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 514, in get_distribution
    dist = get_provider(dist)
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 394, in get_provider
    return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 674, in find
    raise VersionConflict(dist, req)
pkg_resources.VersionConflict: (pytest 2.7.1 (/home/snim2/.local/lib/python2.7/site-packages), Requirement.parse('pytest==2.6.3'))

$ 

So your original pytest is installed system wide, but then you're installing another pytest in .local with your pip --user flag. You need /home/$USER/.local/bin in your PATH - ahead of /usr/bin. Then the second pytest you've installed should be picked up first.
Alternatively, run your pip command without --user (and probably need sudo) then everything is system wide.
Or best of all, use virtualenv!
I've typed this on a phone so sorry for typos.

Thanks. I think I tried apt-get purge python-pytest and installing everything with pip also, and that also failed. It's very confusing having all these different ways of installing things :(