cmd/go: slightly less confusing error message If the argument to go fix isn't a package directory, the message said nothing helpful. Now it at least says a package couldn't be found.
cmd/go: slightly less confusing error message
If the argument to go fix isn't a package directory, the message said nothing helpful.
Now it at least says a package couldn't be found.

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/5577072

mhennings/marcohennings-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,bryanxu/go-zh,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,rdp/rogerpack2005-golang,Triskite/willstone-goclone,Triskite/willstone-goclone,bryanxu/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,d0f/go-zh,Triskite/willstone-goclone,scirelli/scirelli-go,webfd/go-zh,scirelli/scirelli-go,sanjosh/sanjos100-tipc,scirelli/scirelli-go,scirelli/scirelli-go,mhennings/marcohennings-go,scirelli/scirelli-go,Triskite/willstone-goclone,scirelli/scirelli-go,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,scirelli/scirelli-go,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,webfd/go-zh,d0f/go-zh,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,bryanxu/go-zh,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,mhennings/marcohennings-go,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,d0f/go-zh,scirelli/scirelli-go,Triskite/willstone-goclone,rdp/rogerpack2005-golang,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,webfd/go-zh,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,bryanxu/go-zh