Trying to fix appveyor failure:
```
Obtaining file:///C:/projects/tahoe-lafs
Complete output from command python setup.py egg_info:
warning: no previously-included files found matching 'pyproject.toml'
Installed c:\projects\tahoe-lafs\.eggs\setuptools-41.0.1-py2.7.egg
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\projects\tahoe-lafs\setup.py", line 297, in <module>
**setup_args
File "c:\python27\Lib\distutils\core.py", line 111, in setup
_setup_distribution = dist = klass(attrs)
File "C:\projects\tahoe-lafs\.tox\coverage\lib\site-packages\setuptools\dist.py", line 272, in __init__
_Distribution.__init__(self,attrs)
File "c:\python27\Lib\distutils\dist.py", line 287, in __init__
self.finalize_options()
File "C:\projects\tahoe-lafs\.tox\coverage\lib\site-packages\setuptools\dist.py", line 327, in finalize_options
ep.load()(self, ep.name, value)
File "C:\projects\tahoe-lafs\.tox\coverage\lib\site-packages\pkg_resources\__init__.py", line 2202, in load
return self.resolve()
File "C:\projects\tahoe-lafs\.tox\coverage\lib\site-packages\pkg_resources\__init__.py", line 2212, in resolve
raise ImportError(str(exc))
ImportError: 'module' object has no attribute 'check_specifier'
```
"tahoe run" has no quiet option so `test_client_no_noise` is not applicable.
This is a loss of the coverage of the quiet option for `tahoe start`. That is
unfortunate but fixing any `tahoe start`-using test is really hard and the
functionality that is no longer covered is so trivial it hardly seems like it
made sense to test it by running multiple tahoe child processes anyway.
