bug#55440: pytest2-cov is broken, breaking wicd

[Leo Famulari <leo@famulari.name>]

Between commits
2e0d02ebe351024cd97911cb1e5e1a6af1edc7f0..93baba64753d4f8543b38a3a6092b7a71b79b246,
the pytest2-cov package broke, which in turns breaks the important
package wicd.

https://ci.guix.gnu.org/build/791078/details

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starting phase `build'
running "python setup.py" with command "build" and parameters ()
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "setup.py", line 87, in <module>
    long_description='{}\n{}'.format(read('README.rst'), re.sub(':[a-z]+:`~?(.*?)`', r'``\1``', read('CHANGELOG.rst'))),
  File "setup.py", line 23, in read
    encoding=kwargs.get('encoding', 'utf8')
TypeError: 'encoding' is an invalid keyword argument for this function
error: in phase 'build': uncaught exception:
%exception #<&invoke-error program: "python" arguments: ("-c" "import setuptools, tokenize;__file__='setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\\r\\n', '\\n');f.close();exec(compile(code, __file__, 'exec'))" "build") exit-status: 1 term-signal: #f stop-signal: #f> 
phase `build' failed after 0.3 seconds
command "python" "-c" "import setuptools, tokenize;__file__='setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\\r\\n', '\\n');f.close();exec(compile(code, __file__, 'exec'))" "build" failed with status 1
builder for `/gnu/store/gdmcpvplhj91149grnwc443fhbmi3jfv-python2-pytest-cov-3.0.0.drv' failed with exit code 1
build of /gnu/store/gdmcpvplhj91149grnwc443fhbmi3jfv-python2-pytest-cov-3.0.0.drv failed
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