Error when reading MSG native format

[ColinDuff]

When trying to load an MSG LEV15 native format file i get the following error

[DEBUG: 2018-02-13 11:29:32 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/tcenas/home/cduff/MPEF/MPEF_MSG_TOOLS/PYTROLL_DEVELOPMENT/satpy/satpy/etc'
[DEBUG: 2018-02-13 11:29:32 : satpy.readers] Reading ['/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/etc/readers/native_msg.yaml', '/tcenas/home/cduff/MPEF/MPEF_MSG_TOOLS/PYTROLL_DEVELOPMENT/satpy/satpy/etc/readers/native_msg.yaml', '/tcenas/home/cduff/MPEF/MPEF_MSG_TOOLS/PYTROLL_DEVELOPMENT/satpy/satpy/etc/readers/native_msg.yaml']      
[DEBUG: 2018-02-13 11:29:33 : satpy.readers.yaml_reader] Assigning to native_msg: ['/tcenas/home/cduff/PYTROLL_DEV/MSG3-SEVI-MSG15-0100-NA-20170913002740.946000000Z-20170326102757-1214004.nat']
Traceback (most recent call last):
  File "native_msg_test.py", line 26, in <module>
    filenames=[path+fname]
  File "/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/scene.py", line 143, in __init__
    reader_kwargs=reader_kwargs)
  File "/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/scene.py", line 188, in create_reader_instances
    ppp_config_dir=self.ppp_config_dir)
  File "/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/readers/__init__.py", line 412, in load_readers
    reader_instance.create_filehandlers(loadables)
  File "/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/readers/yaml_reader.py", line 599, in create_filehandlers
    filename_set)
  File "/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/readers/yaml_reader.py", line 588, in new_filehandlers_for_filetype
    return list(filtered_iter)
  File "/tcenas/home/cduff/PYTROLL_DEV/satpy/satpy/readers/yaml_reader.py", line 562, in filter_fh_by_metadata
    filehandler.metadata['start_time'] = filehandler.start_time
AttributeError: 'NativeMSGFileHandler' object has no attribute 'metadata'

The metadata parameter is not being created in the NativeMSGFileHandler class, init function.

1 solution is to call super.__init for the BaseFileHandler class which will create and assign the metadata parameter.

ie

class NativeMSGFileHandler(BaseFileHandler):

    """Native MSG format reader
    """

    def __init__(self, filename, filename_info, filetype_info):
       """ Code the needs to be added """
        super(NativeMSGFileHandler,self).__init__(filename, 
	                                         filename_info, 
	                                         filetype_info)

Also , we (EUMETSAT) have a different filename format for the native msg data so i would like to update the native_msg yaml reader file_patterns to recognise this format

Colin Duff
EUMETSAT

[sjoro]

Fixed and merged to develop