* Run isort on the codebase

Command: isort --recursive --skip __main__.py --skip _vendor -o pip._vendor -sd THIRDPARTY -m 5 -p pip -p tests ./pip ./tests

* 📰

Add news entry for upgrade-strategy

* Test auto_decode when getpreferredencoding is None

* Fall back to sys.getdefaultencoding in auto_decode

* Add a news file fragment for 4184

* Rename BuildDirectory to TempDirectory

Because that's what it is.

* Use TempDirectory in more places (take 2)

* Fix indentation...

* 🎨

* Dumb mistake.

* Defer creation of temporary directory

* Misc

* Oops!

* Use better name

* Fix mistakes made in rebasing

* Remove unnecessary wrapping

* 📰

* Misc change to trigger a new CI build

* Make TempDirectory more robust

Update test accordingly

* 🎨 Remove unused import

* 🔧 Fix mistake made during merge

* Move kind to prefix

* Move delete initalization to __init__

* Remove unrelated message

* Improve existing test

* Oops.

* Add a test to verify that readonly files are also deleted

* 🎨

* Increase places where TempDirectory is used

* Remove unused import

* Improve tests, fix bug

* 🎨

* Update test for new behaviour

* Missed no_clean argument

* Make temp_dir private

* Delete the temporary directory based on no_clean

* Give TemporaryDirectory use a unique name

* 🎨

* 📝 Add basic documentation

Misc Changes

Indent the completion text and use textwrap.dedent

When reading bytes from subprocesses, use the locale encoding. Don't fail if the data is encoded incorrectly - instead, use the backslashreplace error handler (and warn the user).

Update pyproject.toml for PEP-518

close some more files in the tests

Close files in tests -- fixes warnings

Use str.format to format in the long line.

- non_hierarchical was apparently never used in the standard library
  (and is not provided by six.moves)
- uses_fragment is useless since Python 2.7.5 and 3.2.4
https://github.com/python/cpython/commit/1be320ebdd5b1f46f32e32c83f3c1e982e2d27e2

Use SecureTransport on macOS

fix for 'pretend' and 'scripttest>=1.3' getting concatenated

Switch default upgrade strategy to only-if-needed

Install build dependencies as specified in PEP 518

Older versions of OpenSSL (before 1.0.1) did not support TLSv1.2 and
in the near future PyPI will be configured to *only* support TLSv1.2+.
This allows us to utilize SecureTransport on these systems where the
linked OpenSSL is *not* new enough to handle TLSv1.2.

Upgrade Dependencies

Mark network tests as flaky and do reruns on fail

Nicer permissions error message