Mate not found!

[ryanabo]

File "/data/share/Software/software/BreaKmer-master/breakmer.py", line 104, in
r.run(tic)
File "/data/share/Software/software/BreaKmer-master/sv_processor.py", line 195, in run
if not trgt.get_sv_reads() :
File "/data/share/Software/software/BreaKmer-master/sv_processor.py", line 468, in get_sv_reads
self.extract_bam_reads('sv')
File "/data/share/Software/software/BreaKmer-master/sv_processor.py", line 506, in extract_bam_reads
pair_indices, valid_reads = process_reads(areads, read_d, bamfile)
File "/data/share/Software/software/BreaKmer-master/sv_processor.py", line 32, in process_reads
add_discordant_pe(aread, read_d, bamfile) #
File "/data/share/Software/software/BreaKmer-master/sv_processor.py", line 65, in add_discordant_pe
mate_read = bamfile.mate(aread)
File "csamtools.pyx", line 1011, in pysam.csamtools.Samfile.mate (pysam/csamtools.c:11048)
ValueError: mate not found

the version of python and pysam:
Python 2.7.9 ,pysam-0.7.5