bpo-1635741: Port _dbm module to multiphase initialization

[corona10]

https://bugs.python.org/issue1635741

[corona10]

@shihai1991 PTAL!

[corona10]

I' ve checked the memory leak with these scripts and no leaks found

./python.exe -m test test_dbm -R 3:3 

deftest_dbm(self): code=textwrap.dedent(r""" import glob import test.support dbm = test.support.import_module('_dbm') _fname = test.support.TESTFN def delete_files(): for f in glob.glob(_fname + "*"): test.support.unlink(f) f = dbm.open(_fname, 'n') f[b'g'] = b"indented" f.close() delete_files() """) ret=test.support.run_in_subinterp(code) self.assertEqual(ret, 0)

[corona10]

@shihai1991 Thanks shihai! I've updated it

[shihai1991]

Thanks, LGTM.

[bedevere-bot]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[corona10]

I have made the requested changes; please review again

[vstinner]

Thanks! It's now much better!

[vstinner]

LGTM, thanks!