Doesn't support extra format for pip package name

[Stony Wang]

python {
    pip 'requests[socks,security]:2.18.4'
}

10:34:12 :pipInstall FAILED
10:34:12 
10:34:12 FAILURE: Build failed with an exception.
10:34:12 
10:34:12 * What went wrong:
10:34:12 Could not evaluate onlyIf predicate for task ':pipInstall'.
10:34:12 > Incorrect pip module declaration (must be 'module:version'): pip
10:34:12 
10:34:12 * Try:
10:34:12 Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
10:34:12 
10:34:12 * Get more help at https://help.gradle.org

It works well when:

python {
    pip 'requests:2.18.4'
}