prompt: don't crash on missing /etc/passwd

lib/prompt.py

@@ -220,16 +220,20 @@ class LoginPart(Part):
 		self.fragments.append(style_reset())
 
 def list_homes():
-	already_listed = set()
+	usernames = []
+	home_dirs = []
 	
+	if os.path.exists("/etc/passwd"):
 		with open("/etc/passwd") as f:
 			for line in f:
 				tokens = line.split(":")
 				
 				if tokens[5] != "/dev/null":
-				if tokens[5] not in already_listed:
-					already_listed.add(tokens[5])
-					yield (tokens[5], tokens[0])
+					if tokens[5] not in home_dirs:
+						usernames.append(tokens[0])
+						home_dirs.append(tokens[5])
+	
+	return list(zip(home_dirs, usernames))
 
 class Dir:
 	def __init__(self, path, name=None, slash="/"):