Improve module not found error message in case of missing version

[quintesse]

On the mailing list a user got misled by the message that a module in a HTTP repository could not be found while it was clearly there. They were used to the fact that you can leave out a version and Ceylon will either automatically choose the only one available or give you the list of possibilities.

Thing is this doesn't work for repositories that can't be searched, like plain (non Herd) HTTP repositories.

We should improve this error in those cases by suggesting to specify a version.

[quintesse]

Done, will now show something like:

$ ceylon run --rep http://lucaswerkmeister.github.io/ceylon.formatter/modules/ ceylon.formatter
ceylon run: Module ceylon.formatter not found in the following repositories:
    /home/ceylon/ceylon/ceylon-dist/dist/repo
    /home/ceylon/ceylon/ceylon-eclipse-workspace/compiler-test/modules
    /home/ceylon/.ceylon/cache
    /home/ceylon/.ceylon/repo
    http://modules.ceylon-lang.org/repo/1
    /home/ceylon/.ceylon/cache
Not all repositories could be searched for matching modules/versions, try again using a specific version

See how the lucaswerkmeister repo doesn't even show up because it hasn't been searched. If on the other hand you specify a version but the wrong one you'll get:

$ ceylon run --rep http://lucaswerkmeister.github.io/ceylon.formatter/modules/ ceylon.formatter/1.2.3
ceylon run: Module ceylon.formatter not found in the following repositories:
    /home/ceylon/ceylon/ceylon-dist/dist/repo
    /home/ceylon/ceylon/ceylon-eclipse-workspace/compiler-test/modules
    /home/ceylon/.ceylon/cache
    http://lucaswerkmeister.github.io/ceylon.formatter/modules/
    /home/ceylon/.ceylon/repo
    http://modules.ceylon-lang.org/repo/1
    /home/ceylon/.ceylon/cache

And the extra suggestion to specify a version won't show.

Hope this will help/unconfuse people.

[lucaswerkmeister]

Thanks!