ctypes.util assumes several things of its environment which sometimes
don't hold:

  * It depends on objdump being in $PATH.  If it isn't, it will fail to
read the SONAME from a library, even if it has determined the path to it.
  * If it uses ldconfig (which, unlike objdumb, it assumes it knows the
full path to and doesn't rely on $PATH to find), it fails to interpret
the results because the regular expression it applies doesn't define any
groups.

The attached patch is what I used to work around these issues in one
particular environment.  I don't claim the fixes to be general, and the
patch includes no unit tests.