xonsh-0.6.2/
[...]
  File "/tmp/guix-build-xonsh-0.6.2.drv-0/xonsh-0.6.2/xonsh/parser.py", line 10,
 in Parser
    from xonsh.parsers.v36 import Parser as p
  File "/tmp/guix-build-xonsh-0.6.2.drv-0/xonsh-0.6.2/xonsh/parsers/v36.py", lin
e 4, in <module>
    from xonsh.parsers.v35 import Parser as ThreeFiveParser
  File "/tmp/guix-build-xonsh-0.6.2.drv-0/xonsh-0.6.2/xonsh/parsers/v35.py", lin
e 4, in <module>
    from xonsh.parsers.base import BaseParser
  File "/tmp/guix-build-xonsh-0.6.2.drv-0/xonsh-0.6.2/xonsh/parsers/base.py", li
ne 18, in <module>
    from xonsh.lexer import Lexer, LexToken
  File "/tmp/guix-build-xonsh-0.6.2.drv-0/xonsh-0.6.2/xonsh/lexer.py", line 16, 
in <module>
    from xonsh.tokenize import (OP, IOREDIRECT, STRING, DOLLARNAME, NUMBER,
  File "/tmp/guix-build-xonsh-0.6.2.drv-0/xonsh-0.6.2/xonsh/tokenize.py", line 5
7, in <module>
    ASYNC = token.ASYNC
AttributeError: module 'token' has no attribute 'ASYNC'