bug#32593: bad error message when kernel module does not exist

[Ricardo Wurmus]

When a system is built that requests a kernel module that does not
exists, this is the error message a user will see:

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Backtrace:
           8 (primitive-load "/gnu/store/vz7ci9rh483f2zps2cl174rd91b?")
In ice-9/eval.scm:
    619:8  7 (_ #f)
   626:19  6 (_ #<directory (guile-user) 7cf140>)
    159:9  5 (_ _)
In gnu/build/linux-modules.scm:
   184:47  4 (recursive-module-dependencies _ #:lookup-module _)
    98:14  3 (module-dependencies _)
    85:18  2 (modinfo-section-contents _)
In ice-9/ports.scm:
   439:11  1 (call-with-input-file #f #<procedure get-bytevector-al?> ?)
In unknown file:
           0 (open-file #f "r" #:encoding #f #:guess-encoding #f)

ERROR: In procedure open-file:
Wrong type (expecting string): #f
builder for `/gnu/store/0ahsvp7wx52zzh1rywbdbq78llcwb7id-linux-modules.drv' 
failed with exit code 1
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-- 
Ricardo