bpftool doc man page build failure

[Yonghong Song <yhs@xxxxxx>]

Quentin,

I hit the following errors with latest bpf-next.

-bash-4.4$ make man
   GEN      bpftool-perf.8
   GEN      bpftool-map.8
   GEN      bpftool.8
   GEN      bpftool-net.8
   GEN      bpftool-feature.8
   GEN      bpftool-prog.8
   GEN      bpftool-cgroup.8
   GEN      bpftool-btf.8
   GEN      bpf-helpers.rst
Parsed description of 111 helper function(s)
Traceback (most recent call last):
   File "../../../../scripts/bpf_helpers_doc.py", line 421, in <module>
     printer.print_all()
   File "../../../../scripts/bpf_helpers_doc.py", line 187, in print_all
     self.print_one(helper)
   File "../../../../scripts/bpf_helpers_doc.py", line 378, in print_one
     self.print_proto(helper)
   File "../../../../scripts/bpf_helpers_doc.py", line 356, in print_proto
     proto = helper.proto_break_down()
   File "../../../../scripts/bpf_helpers_doc.py", line 56, in 
proto_break_down
     'type' : capture.group(1),
AttributeError: 'NoneType' object has no attribute 'group'
make: *** [bpf-helpers.rst] Error 1
-bash-4.4$ pwd
/home/yhs/work/net-next/tools/bpf/bpftool/Documentation
-bash-4.4$

Maybe a format issue in the comments with some recent helpers?

Thanks,

Yonghong