@@ -918,23 +918,33 @@ def _validate_linestyle(ls):
918918 if isinstance (ls , six .string_types ):
919919 try :
920920 return _validate_named_linestyle (ls )
921- except KeyError :
922- pass
923-
924- # On-off ink (in points) sequence *of even length*.
921+ except (UnicodeDecodeError , KeyError ):
922+ # On Python 2, string-like *ls*, like for example
923+ # 'solid'.encode('utf-16'), may raise a unicode error.
924+ raise ValueError ("the linestyle string is not a valid string." )
925+
926+ if hasattr (ls , 'decode' ):
927+ # On Python 2, a string-like *ls* should already have lead to a
928+ # successful return or to raising an exception. On Python 3, we have
929+ # to manually raise an exception in the case of a byte-like *ls*.
930+ # Otherwise, if *ls* is of even-length, it will be passed to the
931+ # instance of validate_nseq_float, which will return an absurd on-off
932+ # ink sequence...
933+ raise ValueError ("linestyle neither looks like an on-off ink sequence "
934+ "nor a valid string." )
935+
936+ # Look for an on-off ink sequence (in points) *of even length*.
925937 # Offset is set to None.
926938 try :
927939 if len (ls ) % 2 != 0 :
928- # Expecting a sequence of even length
929- raise ValueError
940+ raise ValueError ( "the linestyle sequence is not of even length." )
941+
930942 return (None , validate_nseq_float ()(ls ))
931- except (ValueError , TypeError ):
932- # TypeError can be raised by wrong types passed to float()
933- # (called inside the instance of validate_nseq_float).
934- pass
935943
936- raise ValueError ("linestyle must be a valid string or "
937- "an even-length sequence of floats." )
944+ except (ValueError , TypeError ):
945+ # TypeError can be raised inside the instance of validate_nseq_float,
946+ # by wrong types passed to float(), like NoneType.
947+ raise ValueError ("linestyle is not a valid on-off ink sequence." )
938948
939949
940950# a map from key -> value, converter
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