CodeReview: Added a canConnect() function to the SubversionAdaptor class. This returns a boolean value indicating whether it is possible to connect to the repository. I have also updated svnImport.php to check this before attempting an update, so more meaningful error messages are output if a connection is not possible (e.g. the network is down).
I have only filled in the contents of this function for the SubversionShell class, as that is the one I am familiar with and am able to test. The other two sub-classes of (SubversionPecl and SubversionProxy) just have dummy functions for now, which always return true. I'll leave it for someone else to fill those in.