:param str_: string to decode

    :rtype: unicode

    :returns: unicode object

    """

    if isinstance(str_, unicode):

        return str_

    if not from_encoding:

        import rhodecode

        DEFAULT_ENCODING = rhodecode.CONFIG.get('default_encoding','utf8')

        from_encoding = DEFAULT_ENCODING

    try:

        return unicode(str_)

    except UnicodeDecodeError:

        pass

    try:

        return unicode(str_, from_encoding)

    except UnicodeDecodeError:

        pass

    try:

        import chardet

        encoding = chardet.detect(str_)['encoding']

        if encoding is None:

            raise Exception()

        return str_.decode(encoding)

    except (ImportError, UnicodeDecodeError, Exception):

        return unicode(str_, from_encoding, 'replace')

def safe_str(unicode_, to_encoding=None):

    """

    safe str function. Does few trick to turn unicode_ into string

    In case of UnicodeEncodeError we try to return it with encoding detected

    by chardet library if it fails fallback to string with errors replaced

    :param unicode_: unicode to encode

    :rtype: str

    :returns: str object

    """

    if not isinstance(unicode_, basestring):

        return str(unicode_)

    if isinstance(unicode_, str):

        return unicode_

    if not to_encoding:

        import rhodecode

        DEFAULT_ENCODING = rhodecode.CONFIG.get('default_encoding','utf8')

        to_encoding = DEFAULT_ENCODING

    try:

        return unicode_.encode(to_encoding)

    except UnicodeEncodeError:

        pass

    try:

        import chardet

        encoding = chardet.detect(unicode_)['encoding']

        print encoding

        if encoding is None:

            raise UnicodeEncodeError()

        return unicode_.encode(encoding)

    except (ImportError, UnicodeEncodeError):

        return unicode_.encode(to_encoding, 'replace')

    return safe_str

def engine_from_config(configuration, prefix='sqlalchemy.', **kwargs):

    """

    Custom engine_from_config functions that makes sure we use NullPool for

    file based sqlite databases. This prevents errors on sqlite. This only

    applies to sqlalchemy versions < 0.7.0

    """

    import sqlalchemy

    from sqlalchemy import engine_from_config as efc

    import logging

    if int(sqlalchemy.__version__.split('.')[1]) < 7:

        # This solution should work for sqlalchemy < 0.7.0, and should use

        # proxy=TimerProxy() for execution time profiling

        from sqlalchemy.pool import NullPool

        url = configuration[prefix + 'url']

        if url.startswith('sqlite'):

            kwargs.update({'poolclass': NullPool})