Issues running `mix docs` - (UndefinedFunctionError) function Makeup.Application

Actually the first time I’m running I am getting a different compilation error. The second time I am getting the one described above. The initial error is:

==> codepagex
Generated codepagex app
Generating docs...
** (UndefinedFunctionError) function :earmark_parser_string_lexer.string/1 is undefined (module :earmark_parser_string_lexer is not available)
    (earmark_parser 1.4.39) :earmark_parser_string_lexer.string(~c"An error returned by Codepagex")
    (earmark_parser 1.4.39) lib/earmark_parser/helpers/leex_helpers.ex:20: EarmarkParser.Helpers.LeexHelpers.tokenize/2
    (earmark_parser 1.4.39) lib/earmark_parser/helpers/lookahead_helpers.ex:16: EarmarkParser.Helpers.LookaheadHelpers.opens_inline_code/1
    (earmark_parser 1.4.39) lib/earmark_parser/parser.ex:658: EarmarkParser.Parser._inline_or_text?/2
    (earmark_parser 1.4.39) lib/earmark_parser/parser.ex:486: EarmarkParser.Parser._consolidate_para/4
    (earmark_parser 1.4.39) lib/earmark_parser/parser.ex:215: EarmarkParser.Parser._parse/4
    (earmark_parser 1.4.39) lib/earmark_parser/parser.ex:68: EarmarkParser.Parser.lines_to_blocks/3
    (earmark_parser 1.4.39) lib/earmark_parser/parser.ex:60: EarmarkParser.Parser.parse_lines/3