Tests fail on pypy3 when berkdb is not installed

[mgorny]

==================================================================== FAILURES =====================================================================
____________________________________________________________ test_move_items[dbm_ndbm] ____________________________________________________________

item_name = 'dbm_ndbm'

    @pytest.mark.parametrize("item_name",
                              [item.name for item in six._moved_attributes])
    def test_move_items(item_name):
        """Ensure that everything loads correctly."""
        try:
>           item = getattr(six.moves, item_name)

test_six.py:121: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../six-1.14.0-pypy3/lib/six.py:92: in __get__
    result = self._resolve()
../six-1.14.0-pypy3/lib/six.py:115: in _resolve
    return _import_module(self.mod)
../six-1.14.0-pypy3/lib/six.py:82: in _import_module
    __import__(name)
/usr/lib/pypy3.6/lib-python/3/dbm/ndbm.py:3: in <module>
    from _dbm import *
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

    import os
    import sys
    import ctypes.util
    from ctypes import Structure, c_char, c_char_p, c_int, c_void_p, CDLL, POINTER
    
    class error(IOError):
        def __init__(self, msg):
            self.msg = msg
    
        def __str__(self):
            return self.msg
    
    class datum(Structure):
        _fields_ = [
        ('dptr', POINTER(c_char)),
        ('dsize', c_int),
        ]
    
        def __init__(self, text):
            if isinstance(text, str):
                text = text.encode(sys.getdefaultencoding())
            elif not isinstance(text, bytes):
                msg = "dbm mapping keys must be a string or bytes object, not {!r}"
                raise TypeError(msg.format(type(text).__name__))
            Structure.__init__(self, text, len(text))
    
    class dbm(object):
        def __init__(self, dbmobj):
            self._aobj = dbmobj
    
        def close(self):
            if not self._aobj:
                raise error('DBM object has already been closed')
            getattr(lib, funcs['close'])(self._aobj)
            self._aobj = None
    
        def __del__(self):
            if self._aobj:
                self.close()
    
        def keys(self):
            if not self._aobj:
                raise error('DBM object has already been closed')
            allkeys = []
            k = getattr(lib, funcs['firstkey'])(self._aobj)
            while k.dptr:
                allkeys.append(k.dptr[:k.dsize])
                k = getattr(lib, funcs['nextkey'])(self._aobj)
            return allkeys
    
        def get(self, key, default=None):
            if not self._aobj:
                raise error('DBM object has already been closed')
            dat = datum(key)
            k = getattr(lib, funcs['fetch'])(self._aobj, dat)
            if k.dptr:
                return k.dptr[:k.dsize]
            if getattr(lib, funcs['error'])(self._aobj):
                getattr(lib, funcs['clearerr'])(self._aobj)
                raise error("")
            return default
    
        def __len__(self):
            return len(self.keys())
    
        def __getitem__(self, key):
            value = self.get(key)
            if value is None:
                raise KeyError(key)
            return value
    
        def __setitem__(self, key, value):
            if not self._aobj:
                raise error('DBM object has already been closed')
            dat = datum(key)
            data = datum(value)
            status = getattr(lib, funcs['store'])(self._aobj, dat, data, lib.DBM_REPLACE)
            if getattr(lib, funcs['error'])(self._aobj):
                getattr(lib, funcs['clearerr'])(self._aobj)
                raise error("")
            return status
    
        def setdefault(self, key, default=''):
            if not self._aobj:
                raise error('DBM object has already been closed')
            dat = datum(key)
            k = getattr(lib, funcs['fetch'])(self._aobj, dat)
            if k.dptr:
                return k.dptr[:k.dsize]
            data = datum(default)
            status = getattr(lib, funcs['store'])(self._aobj, dat, data, lib.DBM_INSERT)
            if status < 0:
                getattr(lib, funcs['clearerr'])(self._aobj)
                raise error("cannot add item to database")
            return default
    
        def __contains__(self, key):
            if not self._aobj:
                raise error('DBM object has already been closed')
            dat = datum(key)
            k = getattr(lib, funcs['fetch'])(self._aobj, dat)
            if k.dptr:
                return True
            return False
        has_key = __contains__
    
        def __delitem__(self, key):
            if not self._aobj:
                raise error('DBM object has already been closed')
            dat = datum(key)
            status = getattr(lib, funcs['delete'])(self._aobj, dat)
            if status < 0:
                raise KeyError(key)
    
        def __enter__(self):
            return self
    
        def __exit__(self, *exc_info):
            self.close()
    
    
    ### initialization: Berkeley DB versus normal DB
    
    def _init_func(name, argtypes=None, restype=None):
        try:
            func = getattr(lib, '__db_ndbm_' + name)
            funcs[name] = '__db_ndbm_' + name
        except AttributeError:
            func = getattr(lib, 'dbm_' + name)
            funcs[name] = 'dbm_' + name
        if argtypes is not None:
            func.argtypes = argtypes
        if restype is not None:
            func.restype = restype
    
    if sys.platform != 'darwin':
        libpath = ctypes.util.find_library('db')
        if not libpath:
            # XXX this is hopeless...
            for c in ['5.3', '5.2', '5.1', '5.0', '4.9', '4.8', '4.7', '4.6', '4.5']:
                libpath = ctypes.util.find_library('db-%s' % c)
                if libpath:
                    break
            else:
>               raise ImportError("Cannot find dbm library")
E               ImportError: Cannot find dbm library

/usr/lib/pypy3.6/lib_pypy/_dbm.py:145: ImportError
================================================ 1 failed, 183 passed, 16 skipped in 25.82 seconds ================================================