Mark up Unicode string

    Running Sphinx v1.4.8
    WARNING: the config value 'copyright' is set to a string with non-ASCII characters; this can lead to Unicode errors occurring. Please use Unicode strings, e.g. u'Content'.
    [...]
    Encoding error:
    'ascii' codec can't decode byte 0xc3 in position 23: ordinal not in range(128)

docs/conf.py

@@ -42,7 +42,7 @@ master_doc = 'index'
 
 # General information about the project.
 project = 'Borg - Deduplicating Archiver'
-copyright = '2010-2014 Jonas Borgström, 2015-2018 The Borg Collective (see AUTHORS file)'
+copyright = u'2010-2014 Jonas Borgström, 2015-2018 The Borg Collective (see AUTHORS file)'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the