BigQuery: doesn't declare dependency on concurrent.futures

[drigz]

bigquery/client.py imports concurrent.futures but it doesn't declare the dependency in setup.py. It should have a declaration like the one from google-cloud-core==0.27.1 (removed in 0.28.0).

Currently this is doesn't break anything because api-core depends on futures, but if that dependency disappears it will break.

This may be true for other clients, I haven't checked. I ran into it when looking at bazelbuild/rules_python#14.

[dhermes]

@jonparrott (our resident packaging expert) WDYT here?

I am inclined to say this is "working as intended".

[theacodes]

Yes, I consider this working as intended. BigQuery does directly import concurrent.futures, so an argument could be made for having a direct dependency.

[lukesneeringer]

Hold on: concurrent.futures is not in the standard library in Python 2.7.

That means that either the BigQuery library only supports 3.4+, or we do need this, yes?

$ python2.7
Python 2.7.10 (default, Feb  7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from concurrent.futures import Future
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named concurrent.futures
>>> ^D

[lukesneeringer]

Oh wait, I spoke too soon. Transitive dependency.

I do not love this generally, but considering we control google.api_core and our tests will fail if we ever make a change, yes this is fine.

If we did not control the dependency, it would not be fine.