Compilation does not stop on XeTeX error

Short: This bug is important for building in an automated manner, because an error in the documentations Tex code currently results in an interactive shell.

I am compiling GHC 8.0.1 and the build system picked up XeTeX, which results in compilation of a PDF. There is a syntax error in the Tex code. Unfortunately, xelatex is called without the -halt-on-error option and compilation just sits there in the interactive xelatex promt.

[...]
generating indices... genindexcd docs/users_guide/build-pdf/users_guide ; xelatex users_guide.tex

writing additional pages... searchThis is XeTeX, Version 3.14159265-2.6-0.99992 (TeX Live 2015/Exherbo texlive-core-2
015-r2) (preloaded format=xelatex)
 restricted \write18 enabled.

copying images... [100%] images/prof_scc.svg                                                                        
copying static files... done
copying extra files... done
dumping search index in English (code: en) ... done
dumping object inventory... done
build succeeded, 25 warnings.
entering extended mode
(./users_guide.tex
LaTeX2e <2015/01/01>
Babel <3.9l> and hyphenation patterns for 79 languages loaded.
(./sphinxmanual.cls
Document Class: sphinxmanual 2009/06/02 Document class (Sphinx manual)
(/usr/share/texmf-dist/tex/latex/base/report.cls
Document Class: report 2014/09/29 v1.4h Standard LaTeX document class
(/usr/share/texmf-dist/tex/latex/base/size10.clo)))
(/usr/share/texmf-dist/tex/generic/iftex/iftex.sty)
(/usr/share/texmf-dist/tex/latex/cmap/cmap.sty

Package cmap Warning: pdftex not detected - exiting.

) (/usr/share/texmf-dist/tex/latex/base/fontenc.sty
[...]
LaTeX Warning: Reference `glasgow_exts:ghc-flag--XIncoherentInstances' on page 
285 undefined on input line 26759.

! Missing \endcsname inserted.
<to be read again> 
                   \let 
l.26762 \begin{Verbatim}[commandchars=\\\{\}]
                                             
?

Please consider adding -halt-on-error in rules/sphinx.mk. Attached is a patch for master.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System
Test case
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