Data directory must exist, doesn't create it itself

[karalabe]

If the data directory I specify does not exist, pyethapp dies a horrible death. This is very annoying for custom network where I just want to point pyethapp to a custom folder (that doesn't exist), and instead of creating it, pyethapp just blows up inside leveldb:

[...]

  File "/usr/lib/python2.7/site-packages/pyethapp-1.5.0-py2.7.egg/pyethapp/app.py", line 223, in run
    service.register_with_app(app)
  File "/usr/lib/python2.7/site-packages/devp2p-0.9.2-py2.7.egg/devp2p/service.py", line 47, in register_with_app
    s = klass(app)
  File "/usr/lib/python2.7/site-packages/pyethapp-1.5.0-py2.7.egg/pyethapp/db_service.py", line 45, in __init__
    self.db_service = dbs[impl](app)
  File "/usr/lib/python2.7/site-packages/pyethapp-1.5.0-py2.7.egg/pyethapp/leveldb_service.py", line 165, in __init__
    LevelDB.__init__(self, dbfile)
  File "/usr/lib/python2.7/site-packages/pyethapp-1.5.0-py2.7.egg/pyethapp/leveldb_service.py", line 74, in __init__
    self.db = leveldb.LevelDB(dbfile, max_open_files=self.max_open_files)
leveldb.LevelDBError: IO error: /root/.config/pyethapp/devcon/leveldb/LOCK: No such file or directory