UnboundLocalError: local variable 'OTU' referenced before assignment

[Biscuite-wzy]

Hi,
When I used this script, I met the following mistakes,

Traceback (most recent call last):
File "/home/xh/Utensils-master/geneStitcher.py", line 132, in
D=Fasta_Parser(File)
File "/home/xh/Utensils-master/geneStitcher.py", line 70, in Fasta_Parser
Records[OTU].Seq = Seq
UnboundLocalError: local variable 'OTU' referenced before assignment

How can I solve it? Thanks