Makes the arrivals shuttle more robust (#2565)

It's harder to mess with the shuttle and after failing to return so many times it boots people off. It also connects the airlocks to distro and gives it a backup canister.

code/modules/shuttles/shuttle_arrival.dm

@@ -20,10 +20,28 @@
 			return	//someone cancelled the launch
 
 		if (at_station() && forbidden_atoms_check())
-			//cancel the launch because of forbidden atoms. announce over supply channel?
+			//cancel the launch because of forbidden atoms
 			moving_status = SHUTTLE_IDLE
 			global_announcer.autosay("Unacceptable items detected aboard the arrivals shuttle. Launch attempt failed. Restarting launch in one minute.", "Arrivals Shuttle Oversight")
 			SSarrivals.set_launch_countdown(60)
+			SSarrivals.failreturnnumber++
+			if(SSarrivals.failreturnnumber >= 2) // get off my shuttle fool
+				var/list/mobstoyellat = mobs_in_area(get_location_area(location))
+				if (!mobstoyellat || !mobstoyellat.len)
+					return
+				for(var/mob/living/A in mobstoyellat)
+					A <<"<span class='danger'>You feel as if you shouldn't be on the shuttle.</span>" // give them an angry text
+					if(!A.client && ishuman(A) && SSarrivals.failreturnnumber >= 3) // well they are SSD and holding up the shuttle so might as well.
+						SSjobs.DespawnMob(A)
+						global_announcer.autosay("[A.real_name], [A.mind.role_alt_title], has entered long-term storage.", "Cryogenic Oversight")
+						mobstoyellat -= A // so they don't get told on
+					else if(A.client && ishuman(A) && SSarrivals.failreturnnumber >= 3) // they aren't SSD and are holding up the shuttle so we are booting them.
+						A.forceMove(pick(kickoffsloc))
+						mobstoyellat -= A
+					else if(!ishuman(A) && SSarrivals.failreturnnumber >=4 && !A.client) // remove non-player mobs to keep things rolling
+						qdel(A)
+				if (mobstoyellat)
+					global_announcer.autosay("Current life-forms on shuttle: [english_list(mobstoyellat)].", "Arrivals Shuttle Oversight") // tell on them
 			return
 
 		if (!forbidden_atoms_check() && !at_station())
@@ -33,6 +51,7 @@
 
 		if(!at_station())
 			global_announcer.autosay("Central Command Arrivals shuttle inbound to NSS Aurora II. ETA: one minute.", "Arrivals Shuttle Oversight")
+		SSarrivals.failreturnnumber = 0
 		arrive_time = world.time + travel_time*10
 		moving_status = SHUTTLE_INTRANSIT
 		move(departing, interim, direction)