(cherry picked from commit 504373c5)

Also backport tests for skipitem() and handling errors.

Actually just one fix on the 2.7 branch.

Contributed by Bradley Laney.

(cherry picked from commit 6b490b5d)

(cherry picked from commit 7762e4d3)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

(cherry picked from commit d6d44327)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

Fixed also testing the "always" warning filter.
(cherry picked from commit b796e7dc)
Co-authored-by: Sergey Fedoseev <fedoseev.sergey@gmail.com>

(cherry picked from commit 2a9b8bab).
(cherry picked from commit 7c43b801503c802ed6ea4b811f5bc73791249d94)

Make the change where discussing the CPython implementation of lists and dicts.
(cherry picked from commit 8d412780)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

(cherry picked from commit 9c5ba097)
Co-authored-by: Marcin Niemira <marcin@niemira.net>

[2.7] bpo-33804: Document that the argument for io.TextIOBase.read() is optional (GH-7510). (GH-8171)

(cherry picked from commit b6bb77c2)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

The Opera Browser was using a outdated command line invocation that resulted in an incorrect URL being opened in the browser when requested using the webbrowser module.

* Correct the arguments passed to the Opera Browser when opening a new URL..
(cherry picked from commit 3cf1f154)
Co-authored-by: Bumsik Kim <k.bumsik@gmail.com>

Most of the change involves fixing up the test suite, which previously made
the assumption that there wouldn't be a new line if the input didn't end in
one.

Contributed by Ammar Askar.

(cherry picked from commit c4ef4896)

(cherry picked from commit fc05e68d)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

(cherry picked from commit b4588c2f)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

(cherry picked from commit 831c2972)
Co-authored-by: Sergey Fedoseev <fedoseev.sergey@gmail.com>

When hunting memory leaks using -R 3:3, test_imap_unordered() of
test_multiprocessing leaks randomly a few memory blocks. It is a
false alarm: when testing using -R 3:20 for example, no leak is
detected.

Modify test_imap_unordered() to be closer to test_imap():

* Only test 10 numbers instead of 1000: it's a pool of 4 processes, so
  10 is enough to test at least one number per process
* Use chunksize=100 instead of chunksize=53 to mimick test_imap()

(cherry picked from commit 23401fb9)

Fix passing lists and tuples of strings containing special characters
'"', '\\', '{', '}' and '\n' as options to tkinter.ttk widgets.
(cherry picked from commit 5bb5bbfc)

(cherry picked from commit 23db935b)
Co-authored-by: Zackery Spytz <zspytz@gmail.com>

(cherry picked from commit 62b6cea6)
Co-authored-by: Srinivas Reddy Thatiparthy (శ్రీనివాస్ రెడ్డి తాటిపర్తి) <srinivasreddy@users.noreply.github.com>

(cherry picked from commit 4e21100f)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

* bpo-33718: regrtest: use format_duration() to display failed tests (GH-7686)

* Enhance also format_duration(): work on integers and rounds towards
  +infinity (math.ceil).
* Write unit tests on format_duration()

(cherry picked from commit 4ffe9c2b)

* bpo-33873: regrtest: Add warning on -R 1:3 (GH-7736)

regrtest: Add warning when using less than 3 warmup runs like -R 1:3.

(cherry picked from commit cac4fef8)

* bpo-33873: Fix bug in `runtest.py` and add checks for invalid `-R` parameters (GH-7735)

Fix bug in `Lib/test/libregrtest/runtest.py` that makes running tests an extra time than the specified number of runs.

Add check for invalid --huntrleaks/-R parameters.

(cherry picked from commit 58ed7307)

(cherry picked from commit 4a6e7460)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

Adds references to info about file modes, `time.strftime()`, string formatting
syntaxes, and logging levels.

(cherry picked from commit a8ddf85a)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

(cherry picked from commit c45cb479074b5d25f0d382d3109f527520a9f03c)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

(cherry picked from commit 38cf49bf)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

(cherry picked from commit 9ac11a75)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

The statement is true for Windows (and macOS) also..
(cherry picked from commit c9d43c70)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

Add -g to LDFLAGS when compiling with LTO to get debug symbols.

Set the openssl version to 1.0.2o and fix compiling Tcl.

Fix test_gdbm.test_reorganize() on macOS with gdbm 1.15: add a
larger value to make sure that the file size changes.

(cherry picked from commit 13c79c677f9ec9437c82eda72fa1c2d288d8fceb)

(cherry picked from commit 71ca738f4cd2696d056d0cdb83bebd576f98ccc2)
Co-authored-by: Xiang Zhang <angwerzx@126.com>

(cherry picked from commit 5092439c)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

Make it the same as when one runs 'python'..
(cherry picked from commit 9d49f850)
Co-authored-by: Stéphane Wirtel <stephane@wirtel.be>

Mention that it can be triggered by triple quotes and after specifying decorators.
(cherry picked from commit 68680035)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

" ... access to elements is O(1)."

(cherry picked from commit 7469ff50)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>