Connecting to a corrupt DB throws an exception

[LefterisJP]

Problem Definition

If the DB is corrupt for some reason then raiden will throw an exception when trying to connect to it.

Traceback (most recent call last):                                                                                                                                                                                                                                              
  File "/usr/lib64/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib64/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/lefteris/ew/raiden/raiden/__main__.py", line 15, in <module>
    main()
  File "/home/lefteris/ew/raiden/raiden/__main__.py", line 11, in main
    run(auto_envvar_prefix='RAIDEN')
  File "/home/lefteris/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/lefteris/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/lefteris/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 1043, in invoke
    return Command.invoke(self, ctx)
  File "/home/lefteris/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/lefteris/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/lefteris/.virtualenvs/raiden/lib/python3.6/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/lefteris/ew/raiden/raiden/ui/cli.py", line 969, in run
    NodeRunner(kwargs, ctx).run()
  File "/home/lefteris/ew/raiden/raiden/ui/cli.py", line 825, in run
    app = self._run_app()
  File "/home/lefteris/ew/raiden/raiden/ui/cli.py", line 843, in _run_app
    app_ = run_app(**self._options)
  File "/home/lefteris/ew/raiden/raiden/ui/cli.py", line 671, in run_app
    discovery=discovery,
  File "/home/lefteris/ew/raiden/raiden/app.py", line 119, in __init__
    discovery=discovery,
  File "/home/lefteris/ew/raiden/raiden/raiden_service.py", line 216, in __init__
    self.start()
  File "/home/lefteris/ew/raiden/raiden/raiden_service.py", line 228, in start
    storage = sqlite.SQLiteStorage(self.database_path, serialize.PickleSerializer())
  File "/home/lefteris/ew/raiden/raiden/storage/sqlite.py", line 22, in __init__
    conn.executescript(DB_SCRIPT_CREATE_TABLES)                                                                                                                                                                                                                                 
sqlite3.DatabaseError: file is not a database                                                                                                                                                                                                                                   
Exception ignored in: <bound method SQLiteStorage.__del__ of <raiden.storage.sqlite.SQLiteStorage object at 0x7f7c5ba5af28>>                                                                                                                                                    
Traceback (most recent call last):
  File "/home/lefteris/ew/raiden/raiden/storage/sqlite.py", line 244, in __del__
    self.conn.close()
AttributeError: 'SQLiteStorage' object has no attribute 'conn'

Task

Print a proper error and quit Raiden. This is a Fatal error and will need manual intervention from the user.