2.7.38: beam-quant-standard.ly fails in "make web"

[Graham Percival]

make external_binary web, osx 10.3.9, etc.  "make web" chokes on this 
file.

lilypond can make beam-quant-standard.ly, but it can't make the 
automatically-generated lily-18blahblah.ly file:

----
spark:~/usr/src/lilypond/input/regression/out-www gperciva$ lilypond 
lily-1852533672.ly
GNU LilyPond 2.7.38
Processing `lily-1852533672.ly'
Parsing...
Renaming input to: `beam-quant-standard.ly'
Interpreting music... [8][16][24][25]
Preprocessing graphical objects...
Calculating line breaks... [3][6][9][12][15][18][21][24][25]
warning: Error in beam quanting.  Expected (2.19,2.19) found (2.81 . 
2.81).
warning: Error in beam quanting.  Expected (-0.19,-0.19) found (0.0 . 
0.0).
warning: Error in beam quanting.  Expected (-0.19,-0.19) found (0.0 . 
0.0).
warning: Error in beam quanting.  Expected (-0.19,-0.19) found (0.0 . 
0.0).
warning: Error in beam quanting.  Expected (3.0,3.0) found (3.5 . 3.5).
error:
The PostScript backend does not support the 'classic'
framework. Use the EPS backend instead,

  lilypond -b eps <file>

or remove the lilypond-book specific settings from the input.
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