update fileHash

the actual function reads a line at a time instead of in fixed chunks,
but this is fine

Randomizer.py

@@ -35,15 +35,19 @@ version = '0.11.6'
 def ceiling(num, denom):
     return -(num // -denom)
 
-def fileHash(fileName):
-    with open(fileName, 'rb') as fh:
-        hash = 0
+def fileHash(file):
+    checksum = 0
+    try:
+        with open(file, 'rb') as source:
             while True:
-            s = fh.read(65536)
+                s = source.read(65536)
                 if not s:
                     break
-            hash = zlib.crc32(s, hash)
-        return (hash & 0xFFFFFFFF)
+                checksum = zlib.crc32(s, checksum)
+    except FileNotFoundError:
+        sys.exit('Error:', file, 'could not be opened.')
+    return checksum & 0xFFFFFFFF
+
 
 def enable_item(graph, item):
     globals()[item] = True