#1295 When mapping contents not exist, error message does not provide enough information

[Hiroshi Miura]

When loading team project with source contents mappings, and one of contents is not exist, project loading failed with error message.
The message dialog and log message in the log file does not provide enough information to fix the issue.

Here is an example of the log;

11:48:40.652: Error: Error updating repository. Skipping. Error: HTTP response code: 404 (TEAM_UPDATE_REPO_ERROR) 
11:48:54.454: Error: Failed to load the specified project. (TF_LOAD_ERROR) 
11:48:54.454: Error: java.lang.RuntimeException: HTTP response code: 404 
11:48:54.454: Error:    at org.omegat.core.team2.impl.HTTPRemoteRepository.retrieve(HTTPRemoteRepository.java:220) 

The log message should provide not only error code also provide URL which cause the error.

[Hiroshi Miura]

https://github.com/omegat-org/omegat/pull/1406