The "gcloud" Python module is now called "google.cloud", so use the new
name.  This means the name of this module needs to change too, since it
can no longer be "google".

This decorator is required to allow Django 1.7 migrations to serialize
instances of this class.  Without the decorator, running "makemigrations"
on code like the following will fail with a "Cannot Serialize" error.

from storages.backends.gcloud import GoogleCloudStorage

gcs = GoogleCloudStorage()

class SomeModel(models.Models):
    some_field = models.FileField(storage=gcs)

According to https://googlecloudplatform.github.io/google-cloud-python/stable/storage-blobs.html#google.cloud.storage.blob.Blob.upload_from_file it's not
actually necessary to specify a MIME type.

We want to use this in the Google Cloud Storage backend as well.

This is a separate commit so we can verify the clean_name tests in s3boto
still pass (before I move those as well).

This is used by s3boto to support the AWS_LOCATION setting, which isn't
needed by Google Cloud Storage

We need this even though we don't have "location" support since it undoes
some of the weirdness (e.g. adding './' at the beginning of some paths)
done by clean_name().

It would be possible to do this more simply but doing it this way makes
things consistent with s3boto.

This is needed so we can detect attempts to open nonexistent files
in read mode.

This fixes test failures caused by compat.py being removed as a result
of dropping Django 1.7 support.

Fixes tests in Python 3.x

`modified_time` always returns a naive datetime.
`get_modified_time`'s return depends on the USE_TZ setting.

* Remove unused argument
* Return filename when file does not exist

This required handling the num_bytes argument explicitly, so that's now
tested.

* Simplify `num_bytes=None` handling
* Make the `gs` warning a `DeprecationWarning`