blockmodel.py: Fix bug with ignore_degrees

8 jobs for master
Status Name Job ID Coverage
  Test
passed job_clang_amd64 #1196
amd64

05:05:12

passed job_clang_amd64_nosh #1200
amd64

05:00:25

passed job_clang_py2_amd64 #1198
amd64

05:01:53

passed job_gcc_386 #1193
i386

08:30:50

passed job_gcc_amd64 #1195
amd64

04:18:30

passed job_gcc_amd64_nosh #1199
amd64

04:04:39

passed job_gcc_py2_386 #1194
i386

07:40:52

passed job_gcc_py2_amd64 #1197
amd64

04:09:55