Reviewers: Jason Gustafson <jason@confluent.io>

Reviewer: Ewen Cheslack-Postava <ewen@confluent.io>

Rather than using sed, use built-in Python regular expressions to strip
the SNAPSHOT expression from the pom.xml files.  Sed has different flags
on different platforms, such as Linux.  Using Python directly here is
more compatible, as well as being more efficient, and not requiring an
rm command afterwards.

When running release_notes.py, use the current Python interpreter.
This is needed to prevent attempting to run release_notes.py with
Python 3 on some systems.  release_notes.py will not (yet) work with
Python 3.

Author: Colin P. Mccabe <cmccabe@confluent.io>

Reviewers: Magnus Edenhill <magnus@edenhill.se>, David Arthur <mumrah@gmail.com>, Manikumar Reddy <manikumar.reddy@gmail.com>

Closes #6198 from cmccabe/release_py

Scala 2.12 has better support for newer Java versions and includes additional
compiler warnings that are helpful during development. In addition, Scala 2.11
hasn't been supported by the Scala community for a long time, the soon to be
released Spark 2.4.0 will finally support Scala 2.12 (this was the main reason
preventing many from upgrading to Scala 2.12) and Scala 2.13 is at the RC stage.
It's time to start recommending the Scala 2.12 build as we prepare support for
Scala 2.13 and start thinking about removing support for Scala 2.11.

In the meantime, Jenkins will continue to build all supported Scala versions (including
Scala 2.11) so the PR and trunk jobs will fail if people accidentally use methods
introduced in Scala 2.12.

Reviewers: Ewen Cheslack-Postava <me@ewencp.org>

Author: Bibin Sebastian <bisebastian@DELC02QP51SG8WN.sea.corp.expecn.com>
Author: Ewen Cheslack-Postava <me@ewencp.org>

Reviewers: Matthias J. Sax <mjsax@apache.org>, Ewen Cheslack-Postava <ewen@confluent.io>

Closes #5572 from bibinss/release_mail

Just a doc change

Author: John Eismeier <john.eismeier@gmail.com>

Reviewers: Ewen Cheslack-Postava <ewen@confluent.io>

Closes #4573 from jeis2497052/trunk

Reviewers: Ismael Juma <ismael@juma.me.uk>, Guozhang Wang <wangguoz@gmail.com>

Reviewers: Ewen Cheslack-Postava <ewen@confluent.io>, Dong Lin <dolin@linkedin.com>

* Set --source, --target and --release to 1.8.
* Build Scala 2.12 by default.
* Remove some conditionals in the build file now that Java 8
is the minimum version.
* Bump the version of Jetty, Jersey and Checkstyle (the newer
versions require Java 8).
* Fixed issues uncovered by the new version if Checkstyle.
* A couple of minor updates to handle an incompatible source
change in the new version of Jetty.
* Add dependency to jersey-hk2 to fix failing tests caused
by Jersey upgrade.
* Update release script to use Java 8 and to take into account
that Scala 2.12 is now built by default.
* While we're at it, bump the version of Gradle, Gradle plugins,
ScalaLogging, JMH and apache directory api.
* Minor documentation updates including the readme and upgrade
notes. A number of Streams Java 7 examples can be removed
subsequently.

Author: Ewen Cheslack-Postava <me@ewencp.org>

Reviewers: Ismael Juma <ismael@juma.me.uk>, Damian Guy <damian.guy@gmail.com>

Closes #3917 from ewencp/stage-docs

Author: Ewen Cheslack-Postava <me@ewencp.org>

Reviewers: Damian Guy <damian.guy@gmail.com>, Ismael Juma <github@juma.me.uk>

Closes #4528 from ewencp/update-release-script

Author: Guozhang Wang <wangguoz@gmail.com>

Reviewers: Ismael Juma <ismael@juma.me.uk>, Ewen Cheslack-Postava <ewen@confluent.io>

Closes #4054 from guozhangwang/KMinor-pre-1.0-release

Author: Damian Guy <damian.guy@gmail.com>

Reviewers: Ismael Juma <ismael@juma.me.uk>, Guozhang Wang <wangguoz@gmail.com>

Closes #3846 from dguy/minor-release-script

As per Apache guidelines:

http://www.apache.org/dev/release-distribution#sigs-and-sums

Author: Ismael Juma <ismael@juma.me.uk>

Reviewers: Damian Guy <damian.guy@gmail.com>

Closes #3844 from ijuma/fix-sha512-naming

Author: Ismael Juma <ismael@juma.me.uk>

Reviewers: Damian Guy <damian.guy@gmail.com>

Closes #3789 from ijuma/ftp-release-py-fixes

Author: Ewen Cheslack-Postava <me@ewencp.org>

Reviewers: Gwen Shapira

Closes #2795 from ewencp/release-script and squashes the following commits:

f1d0590 [Ewen Cheslack-Postava] Don't expose promotion to the user since it is not implemented yet.
1a6947a [Ewen Cheslack-Postava] Handle cleanup if there's a failure during generation of release notes.
fa58401 [Ewen Cheslack-Postava] Fix hard-coded uses of trunk
639bcca [Ewen Cheslack-Postava] Try to cleanup after most failures.
a3a7245 [Ewen Cheslack-Postava] Fix SCRIPT_DIR to be an absolute path so git clones against the REPO work when it is also your cwd
de54c97 [Ewen Cheslack-Postava] Load/save preferences in a .release-settings.json file so you don't have to keep entering the same info repeatedly
b559a61 [Ewen Cheslack-Postava] Check that the user doesn't have any oustanding diffs before starting the rest of the script
ff0b330 [Ewen Cheslack-Postava] Store original starting branch to switch back to instead of using a default.
b793562 [Ewen Cheslack-Postava] Use 2.12 instead of specific Scala version so we use the default 2.12 version.
382b7f9 [Ewen Cheslack-Postava] MINOR: Add a release script that helps generate release candidates.