How to check that import module will succeed?

[Andrey Zherikov]

Is there a way to check whether some module, say "foo", is 
available for import before doing "import foo"?
I want to create a function that imports module if it's available 
or does something else otherwise. So I think the code should look 
something like this:

mixin template my_import(alias module_name)
{
     if(module_name is available)
         mixin("import "~module_name~";");
     else
         pragma(msg, module_name~" is not available");
}

mixin my_import!("std.stdio");      // == import std.stdio
mixin my_import!("unknown_module"); // == pragma(msg, 
"unknown_module is not available")