* upstream/master: (98 commits)
Fallback to zlib extension to unpack gzip on non Windows systems
Zip extension does not provide zlib support
Unified all Windows tests throughout the code.
Added Platform utility and unit test for it.
Remove warnings for non-writable dirs, refs #3588
[doc] add -H flag to sudo commands
use full json content to determine reference, closes#4859
typos
Make sure COMPOSER_AUTH is also loaded in Config, refs #4546
Use proper defaults for IO authentications
Add verbosity input support to IOInterface
Update SolverTest.php
Update broken-deps-do-not-replace.test
Update SolverProblemsException.php
Cleaned up check+conversion that was no longer required.
Cleaner notation for expected exceptions in fixtures.
Introduced more generic, less invasive way to test for exceptions in fixtures, more in line with how phpunit works.
Included unit test for circular root dependencies.
Expanded InstallerTest to support expecting Exceptions by supplying "EXCEPTION" as "--EXPECT--"
Clarified error message and added braces.
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