bug#15283: on guix 0.3 package -e '(@ …)' has to be run twice to install a new package (not build yet)

[Arne Babenhauserheide]

To test the bug, save this file as mercurial.scm: http://bpaste.net/raw/129793/

Now run
 
    GUILE_LOAD_PATH=. guix package -e '(@ (mercurial) hg)'


On the first run I got the following backtrace: 

@ build-succeeded 
/nix/store/9rajwkq02sk4nq7cvrxilbsvxrywh2zs-mercurial-2.7.1.drv -
Backtrace:
In ice-9/boot-9.scm:
 157: 14 [catch #t #<catch-closure 88e540> ...]
In unknown file:
   ?: 13 [apply-smob/1 #<catch-closure 88e540>]
In ice-9/boot-9.scm:
  63: 12 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 432: 11 [eval # #]
In ice-9/boot-9.scm:
2320: 10 [save-module-excursion #<procedure 8becc0 at ice-9/boot-9.scm:3961:3 
()>]
3966: 9 [#<procedure 8becc0 at ice-9/boot-9.scm:3961:3 ()>]
In unknown file:
   ?: 8 [load-compiled/vm 
"/home/arne/.cache/guile/ccache/2.0-LE-8-2.0/usr/local/bin/guix.go"]
In guix/ui.scm:
 475: 7 [run-guix-command package "-e" "(@ (mercurial) hg)"]
In ice-9/boot-9.scm:
 157: 6 [catch srfi-34 #<procedure e98aa0 at guix/ui.scm:153:2 ()> ...]
 157: 5 [catch system-error ...]
In guix/scripts/package.scm:
 951: 4 [#<procedure 17c1570 at guix/scripts/package.scm:937:8 ()>]
 866: 3 [process-actions (# # # #)]
In guix/store.scm:
 483: 2 [build-derivations # #]
 334: 1 [process-stderr #]
In guix/serialization.scm:
  49: 0 [read-int #<input-output: socket 9>]

guix/serialization.scm:49:4: In procedure read-int:
guix/serialization.scm:49:4: In procedure bv-u32-ref: Wrong type argument in 
position 1 (expecting bytevector): #<eof>

The second run succeeds.