[1.5.x] Removed a mention of `Form._errors` from the documentation.

Also removed a sentence that was incorrect: raising a
`ValidationError` inside `Form.clean` doesn't clear the
`cleaned_data` attribute.

Thanks to loic84 and timograham for the review.

Backport of 9aa6d4bdb6618ba4f17acc7b7c0d1462d6cbc718 and
0048ed77c7016a03aed6dbc255a6372f3df2ccd5 from master.
[1.5.x] Propagate get_user_model exception from get_user

Fixes #21439

Backport of 3560ef04 from master.

Conflicts:
	django/contrib/auth/tests/auth_backends.py
[1.5.x] Fixed #21440 -- Typo in topics/http/shortcuts.txt

Thanks olof.bjarnason at gmail.com for the report.

Backport of 6e9e6ca071 from master
[1.5.x] Fixed #21440 -- Typo #2 in topics/http/shortcuts.txt

Thanks alasdair.

Backport of d011714002 from master
[1.5.x] Fixed #21240 -- Added 1.5 release note for OneToOneField/select_related change.

Thanks marcin at sokrates.pl.

Backport of ba63b9895b from master
[1.5.x] Fixed typo in topics/http/sessions.txt.

Backport of 9348fc5628 from master
Fixed missing imports from 16e5fdd9cb8cca4d203b9255a9771b3c370e37d6.
[1.5.x] Fixed the base class note in the Date Views docs.

Backport of 42197e31aa from master
[1.5.x] Recommended setuptools in the reuseable app tutorial.

setuptools has merged with distribute.

Backport of b5eef8535a from master.
Fixed #21468 -- Removed a ModelForm bit that doesn't apply to 1.5.x.

The bit was incorrectly backported with 3860d5e8f814e26baf4deee9258392cd34a4b456.

Thanks to trac user direx for the report and to Loic Bistuer
for his help.
[1.5.x] Fix #20054: Removed links to modwsgi.org.

Backport of 957fcd0c9fc605bbb69e03296aede3b0bac5a8d2 from master.
Removed obsolete deprecation notes.
[1.5.x] Fixed #21490 -- Fixed custom admin URL reverse example.

Thanks glarrain for the report.

Backport of bfe7377adb from master
[1.5.x] Fixed typo in previous commit; refs #21490.

Backport of 03bc0a8ac5 from master
[1.5.x] Fixed #21507 -- Corrected default widget information for FileField

Backport of 70e61310d6 from master
[1.5.x] Fixed #21515 -- Corrected example of template.Context in documentation.

Thanks to trac user oubiga for the report.

Backport of 077af42139db84d88f293ab5eadc989a9169dce1 from master.
[1.5.x] Fixed #21538 -- Added numpy to test/requirements/base.txt

Thanks Tim Graham for the report

Backport of c75dd664c from master
[1.5.x] Fixed #21558 -- Support building CHM files.

Thanks Michał Pasternak.

Backport of cd9e85ec from master.
[1.5.x] Fixed #21594 -- Added note about model formsets deleting objects.

This behavior has been fixed in 65e03a424e. refs #10284.

Backport of de1d5d5df5 from stable/1.6.x.
[1.5.x] Fixed #21539 -- Added example of modelformset_factory's form argument

Backport of 1fa681ee11 from master