$ sbcl
  * (require :asdf)
  NIL
  * (require :clamp)
  ASDF could not load clamp because
  Error while trying to load definition for system clamp from pathname
  ~/Clamp/clamp.asd:
     The name "ASDF-USER" does not designate any package..

  debugger invoked on a LOAD-SYSTEM-DEFINITION-ERROR in thread
  #<THREAD "initial thread" RUNNING {1002998F33}>:
    Error while trying to load definition for system clamp from pathname
    ~/Clamp/clamp.asd:
       The name "ASDF-USER" does not designate any package.

  Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL.

  restarts (invokable by number or by possibly-abbreviated name):
    0: [RETRY                                 ] Retry EVAL of current toplevel form.
    1: [CONTINUE                              ] Ignore error and continue loading file "~/Clamp/clamp.asd".
    2: [ABORT                                 ] Abort loading file "~/Clamp/clamp.asd".
    3: [REINITIALIZE-SOURCE-REGISTRY-AND-RETRY] Retry finding system clamp after
                                                reinitializing the
                                                source-registry.
    4:                                          Exit debugger, returning to top
                                                level.

  ((FLET #:LAMBDA2286 :IN ASDF::LOAD-SYSDEF)
   #<SB-KERNEL:SIMPLE-PACKAGE-ERROR "The name ~S does not designate any package."
     {10049EB763}>)
  0]