Cherry-pick 276051@main (f657af1). rdar://124542328

    [webkitcorepy] Exit AutoInstall.install when disabled
    https://bugs.webkit.org/show_bug.cgi?id=270920
    rdar://124542328

    Reviewed by Elliott Williams.

    AutoInstall.install will fail if the autoinstaller is disabled.
    Programs shouldn't call AutoInstall.install if the autoinstaller
    is disabled, but the program may still complete, so we should
    just print an error message.

    * Tools/Scripts/libraries/webkitcorepy/webkitcorepy/autoinstall.py:
    (AutoInstall.install): Exit and print error if AutoInstall is disabled.

    Canonical link: https://commits.webkit.org/276051@main

Canonical link: https://commits.webkit.org/272448.732@safari-7618-branch

Tools/Scripts/libraries/webkitcorepy/webkitcorepy/autoinstall.py

@@ -668,6 +668,9 @@ def register(cls, package, local=False):
 
     @classmethod
     def install(cls, package):
+        if not cls.enabled():
+            sys.stderr.write("Autoinstaller disabled, but 'install' called\n")
+            return None
         if isinstance(package, str):
             # we want this to throw if it hasn't been previously registered; in the case
             # that this is being called from cls.find_module it should always exist