Can unpack, and happy.cabal is definitely there.  Unfortunately, stack
init or stack build seems to fail with an aeson exception:

AesonException "Error in
$.packages.cassava.constraints.flags['bytestring--lt-0_10_4']: Invalid
flag name: \"bytestring--lt-0_10_4\""


On 12/25/2017 07:53, Michael Snoyman wrote:
> What command are you running to generate this output? Are you able to
> `stack unpack happy && cd happy-* && stack init && stack build`
> successfully?
>
> On Mon, Dec 25, 2017 at 7:29 AM, Dan Burton <danburton.email@gmail.com
> <mailto:danburton.email@gmail.com>> wrote:
>
>     /cc the haskell-stack mailing list.
>
>     On Dec 24, 2017 9:08 AM, "Eric McCorkle" <eric@metricspace.net

>     <mailto:eric@metricspace.net>> wrote:
>
>         Hi folks,
>
>         I'm trying to update my language project to happy >= 9.16, so I
>         can use
>         typeclass-based parsers.  Unfortunately, I'm running into build
>         errors
>         after switching to lts-9.20.  The log file is attached.
>
>         I see similar problems when trying to build alex (the lexer
>         generator).
>
>         It seems to be claiming that there is no cabal file, which is
>         odd, as
>         there clearly is one (in the source at least).
>
>         Has anyone else seen this problem, and if so, what is the
>         workaround?
>
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