Support for the Ruby 2.4 series has ended. See here for reference.
# File psych/lib/psych/syntax_error.rb, line 8 def initialize file, line, col, offset, problem, context err = [problem, context].compact.join ' ' filename = file || '<unknown>' message = "(%s): %s at line %d column %d" % [filename, err, line, col] @file = file @line = line @column = col @offset = offset @problem = problem @context = context super(message) end