Draft a way to fetch metadata from PyPI

.travis.yml

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+branches:
+  only: master
+language: python
+install: pip install tox
+script: tox

tools/make-cheeses.py

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+#!/usr/bin/env python3
+from typing import KeysView
+
+from asks.sessions import Session
+from trio import Nursery, open_nursery, run
+
+PYPI = 'https://pypi.org'
+CONNECTIONS = 20
+
+
+async def culture(session: Session) -> KeysView[str]:
+    """Return the 100 most popular cheeses in cheese shop."""
+    stats = await session.get(
+        path='/stats', headers={'Accept': 'application/json'})
+    return stats.json()['top_packages'].keys()
+
+
+async def drain(project_name: str, version: str, session: Session) -> None:
+    """Fetch metadata of the given distribution."""
+    # XXX: insert the fetched metadata to a database
+    await session.get(path=f'/pypi/{project_name}/{version}/json')
+    print(project_name, version)
+
+
+async def coagulate(project_name: str, nursery: Nursery,
+                    session: Session) -> None:
+    """Fetch project's available versions and the metadata of each."""
+    response = await session.get(path=f'/pypi/{project_name}/json')
+    for version in response.json()['releases'].keys():
+        # Recklessly filter out prereleases
+        for n in version.split('.'):
+            try:
+                int(n)
+            except ValueError:
+                break
+        else:
+            nursery.start_soon(drain, project_name, version, session)
+
+
+async def main(session: Session):
+    """Make cheeses."""
+    async with open_nursery() as nursery:
+        for project_name in await culture(session):
+            nursery.start_soon(coagulate, project_name, nursery, session)
+
+
+if __name__ == '__main__':
+    run(main, Session(PYPI, connections=CONNECTIONS))

tools/requirements.txt

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+asks
+trio

tox.ini

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+[tox]
+envlist = py
+minversion = 3.3
+isolated_build = True
+
+[testenv]
+skip_install = True
+deps =
+    flake8-builtins
+    isort[requirements]
+commands =
+    flake8
+    isort -c --diff
+
+[flake8]
+hang-closing = True
+ignore = W503, E125, E225, E226, E227, E701, E704
+; See https://github.com/PyCQA/pycodestyle/issues/906
+;max-doc-length = 72