Don't throw Exception if "/Packages" cannot be created in Doc-Root
When the new package management takes over throught the Install Tool it tries to create a "Packages" subdirectory directly in PATH_site. This might fail due to no writing rights on this level.
This is not unusual, as TYPO3 never really needed to write anything here, so many installations have hardened their instances by not allowing doc-root-writing.
So we should instead not fatal with an exception, but accept that it wasn't created and not bother about it.