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- Print only warning instead of error, as the module is only optional
- Log the error to the debug log, so users dont think we didnt catch the exception

The HTTPUploadPlugin calls that if encryption is enabled

Call the `encrypt_file` method of the encryption plugin instead

A patch in Gajim made that unnecessary

- unused import
- unused var GAJIM_VERSION
- redundant self.plugin = self
- simplify condition
- redundant 'else'

This happend during porting the plugin to the new encryption API

httpupload version 0.6.2

See merge request !39

ESessions Plugin version 1.0.0

See merge request !36

PGP Plugin version 1.0.0

See merge request !37

omemo version 2.3.0

See merge request !38