There is an existing `SystemCommand.run` that executes command with
`sudo`.  Use that instead of yet another custom wrapper.

In case the parent directory of Caskroom is writable for the user, we
don't need to use `sudo` to execute commands.

Make a generic method to run commands that has an option to switch sudo
so that we can run commands with and without sudo.

Relatively old code in Hbc::Caskroom recursively changes the ownership
of the directory where the Caskroom directory exists, that changes
entire files in /usr/local to user:staff if Homebrew setup with default
configuration.
This is really dangerous because it's easy to trigger (just simply type
`brew cask something` by following some installation documentation.)

This patch removes entire `chown` with -R option and make the logic
simply creating Caskroom directory with default Homebrew directories
ownership and permission.

diagnostic: handle HOMEBREW_TEMP mktmpdir failure.

Fixes #1223.

Comment out `license` stanza deprecation warning.

Revert "Migrate a Formula to Multiple Versions: add docs."

Migrate a Formula to Multiple Versions: add docs.

cleanup: remove GLIDE_HOME cache directories

This is needed since some formulae now set

  ENV["GLIDE_HOME"] = HOMEBREW_CACHE/"glide_home/#{name}"

brew.sh: improve user agent with no git repo.

Rename FormulaMethodDeprecatedError to  MethodDeprecatedError.

Remove Homebrew Cask documentation.

Make parsing locales more robust.

`Homebrew/>1.0.0 (no git repository) (Macintosh; Intel macOS 10.7.5)...)
reads pretty weirdly in a user agent and I've had complaints that `>`
may be an invalid character in some cases.

audit: forbid `deprecated_option` in new formulae

Deprecate license

Make `core_tap_version_string` reusable.

* Fix IntegrationCommandTestCask

“Homebrew Cask” -> “Homebrew-Cask”

Fix exit code for multilingual cask audit.

Change `A Cask for #{token} is already installed.` message.

Add `.com.apple.timemachine.supported` to DMG_METADATA_FILES.

virtualenvs remember the prefix of the python that created them and do
magic to load packages from them; help them remember a more durable
path.

Refactor Cask’s extensions.

Use `module_function` for `Homebrew` module.