Python Support

Hi,

I tried to mirror some python packages but each time I have an error on jupyter-core package, normally when I delete recreate the repository I have it work but not here. Any idea ?

```
[root@repos ~]# pulp-admin -v python repo create --repo-id=vpnssl_pypi --feed https://pypi.python.org/ --proxy-host=http://proxy.local --proxy-port=3128 --package-names setuptools,amqp,aniso8601,appdirs,arrow,asn1crypto,astroid,atomicwrites,attrs,backcall,bandit,beautifulsoup4,billiard,bs4,cached-property,celery,certifi,cffi,chardet,click,colorhash,configparser,CouchDB,coverage,cryptography,dataclasses,decorator,deep_merge,defusedxml,digicert_client,entrypoints,esdk-obs-python,filelock,flake8,flake8-bandit,flake8-colors,flake8-docstrings,flake8-import-order,flake8-polyfill,Flask,Flask-MonitoringDashboard,flask-restplus,Flask-WTF,gitdb2,GitPython,gunicorn,idna,ipython,ipython_genutils,isodate,isort,itsdangerous,jedi,Jinja2,jsonschema,jupyter_core,kombu,lazy-object-proxy,lxml,M2Crypto,MarkupSafe,mccabe,mock,more-itertools,nbformat,numpy,parso,pbr,pep8-naming,pexpect,pickleshare,pip,pipenv,pip-tools,plotly,pluggy,prompt_toolkit,psutil,ptyprocess,py,pycodestyle,pycparser,pydocstyle,pyflakes,Pygments,PyJWT,pylint,pyOpenSSL,pyrsistent,pytest,pytest-cov,pytest-mock,python-consul,python-dateutil,pytz,pyvmomi,PyYAML,redis,requests,requests-toolbelt,retry,setuptools,simplejson,six,smmap2,snowballstemmer,soupsieve,SQLAlchemy,stevedore,toml,tox,traitlets,typed-ast,tzlocal,urllib3,vine,virtualenv,virtualenv-clone,wcwidth,Werkzeug,wheel,wrapt,WTForms,zeep,importlib-metadata,zipp,packaging,pyparsing,designate,pbr,debtcollector,msgpack,netaddr,pyparsing,pytz,Babel,oslo.i18n,netifaces,iso8601,oslo.utils,oslo.serialization,stevedore,rfc3986,slo.config,os-service-types,keystoneauth1,python-keystoneclient,designate,PrettyTable,oslo.upgradecheck,monotonic,fasteners,oslo.concurrency,oslo.context,statsd,WebOb,oslo.middleware,tenacity,python-dateutil,pyinotify,oslo.log,greenlet,dnspython,eventlet,os-win,dogpile.cache,oslo.cache,pycadf,keystonemiddleware,repoze.lru,Routes,python-mimeparse,argparse,linecache2,traceback2,unittest2,extras,testtools,fixtures,PasteDeploy,Yappi,Paste,oslo.service,suds-jurko,Werkzeug,vine,amqp,kombu,cachetools,futurist,oslo.messaging,psutil,oslo.reports,jsonpointer,jsonpatch,appdirs,jmespath,munch,requestsexceptions,asn1crypto,pycparser,cffi,cryptography,openstacksdk,os-client-config,simplejson,colorama,wcwidth,attrs,pyperclip,cmd2,cliff,osc-lib,python-neutronclient,oslo.policy,oslo.rootwrap,waitress,WebTest,logutils,Mako,pecan,dnspython3,jsonschema,python-memcached,click,itsdangerous,Flask,SQLAlchemy,testresources,testscenarios,python-editor,alembic,sqlparse,Tempita,sqlalchemy-migrate,oslo.db,python-designateclient,oslo.versionedobjects,voluptuous,grpcio,tooz,monasca-statsd,designate

[root@repos ~]# pulp-admin -v python repo sync run --repo-id=vpnssl_pypi
----------------------------------------------------------------------
Synchronizing Repository [vpnssl_pypi]
--------------------------------------------------------------------

This command may be exited via ctrl+c without affecting the request.

Downloading Python metadata.
[========================================== ] 85%
186 of 217 items
... failed
Copying units already in pulp
[/]
... completed

Downloading and processing Python packages.
[==================================================] 100%
5690 of 5690 items
... completed

Task Succeeded

Publishing Python Metadata.
[/]

Task Failed

[Errno 17] File exists:
'/var/cache/pulp/reserved_resource_worker-1@repos.engsec/63cb5ed4-e2ee-4163-a532
-8444fa49c2ff/vpnssl_pypi/simple/jupyter-core'
```