old_contents: 
  import cffi
  import os.path
  
  cxx_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'matrixify.cpp')
  with open(cxx_path) as f:
      src = f.read()
  
  ffibuilder = cffi.FFI()
  ffibuilder.set_source('pheweb.load.matrix._matrixify',
                        src,
                        source_extension='.cpp',
                        extra_compile_args=['--std=c++11'],
  )
  ffibuilder.cdef("int cffi_run(int argc, char *argv[]);")
  
new_contents: 
  import cffi
  import os.path
  
  cxx_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'matrixify.cpp')
  with open(cxx_path) as f:
      src = f.read()
  
  ffibuilder = cffi.FFI()
  ffibuilder.set_source('pheweb.load.matrix._matrixify',
                        src,
                        source_extension='.cpp',
                        extra_compile_args=['--std=c++11'],
  )
  ffibuilder.cdef("int cffi_run(char *sites_fname, char *augmented_pheno_glob, char *matrix_fname);")
  
subject: Fix ffibuilder