Improve error reporting from verify_files

Make it similar to what verify_env already does, so that
we tell people exactly which path was a problem.  I hit this
while running salt-master in a non-standard configuration, and
the change makes it easier to hunt down which path is wrong
in a config.
Merge pull request #8193 from jcsp/verify-fix

Improve error reporting from verify_files
Back out earlier fix.
Merge pull request #8202 from cro/fix-4410-again

Back out earlier fix.
Workaround bug in yum python API

This works around a bug in the yum python API where removal of packages
that are required by other packages results in the removal of those
packages as well, and does not raise an exception when errors are
encountered during the transaction test, causing all packages to be
removed.

This commit manually performs the transaction test, and raises an
exception if any errors are found. It also adds a try/except to the
pkg.removed and pkg.purged states which catches the exception and
gracefully returns False without a traceback.

See https://github.com/saltstack/salt/issues/8201 for more information.
Merge pull request #8197 from s0undt3ch/develop

Moved test cases from #8195 to a better place.
Merge pull request #8203 from terminalmage/issue8201

Workaround bug in yum python API
more tabs!
fix function： leaks，serverinfo

#salt 'web-87' tomcat.leaks
web-87:
    F
    a
    i
    l
    e
    d
     
    t
    o
     
    c
    r
    e
    a
    t
    e
     
    H
    T
    T
    P
     
    r
    e
    q
    u
    e
    s
    t

#salt 'web-87' tomcat.serverinfo
web-87:
    ----------
    error:
        F
Document setting a whitelist firewall ruleset on the Master
Merge pull request #8206 from pyinx/patch-2

fix function： leaks，serverinfo
Revert the section title change
Merge pull request #8208 from holmboe/doc-whitelist-firewall

Document setting a whitelist firewall ruleset on the Master
Merge pull request #8209 from holmboe/doc-whitelist-firewall

Revert the section title change
Switch 0.15.1 release notes back to unix line endings

Line endings got switched in 2f869f8. Fixes #8204
Make sure we're getting a dict
Merge pull request #8214 from UtahDave/develop

Make sure we're getting a dict
Updated downloads URL for Windows binaries
More aggressive exception handling and retry logic. Refs #7755.
Import logging.