Bug#917171: FTBFS on all architectures

[Steve McIntyre]

Package: src:haskell-language-python
Version: 0.5.4-7
Severity: serious
Tags: ftbfs

https://buildd.debian.org/status/package.php?p=haskell-language-python
shows current state - failed builds everywhere. Looking at logs,
they're all showing

160 |     parens (pretty (endRow span) <> comma <> pretty (endCol span))
    |                                  ^^

src/Language/Python/Common/SrcLocation.hs:160:43: error:
    Ambiguous occurrence `<>'
    It could refer to either `Prelude.<>',
                             imported from `Prelude' at src/Language/Python/Common/SrcLocation.hs:15:8-41
                             (and originally defined in `GHC.Base')
                          or `Language.Python.Common.Pretty.<>',
                             imported from `Language.Python.Common.Pretty' at src/Language/Python/Common/SrcLocation.hs:37:1-36
                             (and originally defined in `Text.PrettyPrint.HughesPJ')
    |
160 |     parens (pretty (endRow span) <> comma <> pretty (endCol span))
    |                                           ^^
make: *** [/usr/share/cdbs/1/class/hlibrary.mk:147: build-ghc-stamp] Error 1


-- System Information:
Debian Release: 9.6
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-debug'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-8-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)