Silent failure if no bzrdefaults file

[Robert Ladyman]

If the bzrdefaults file does not exist, then operations depending upon it that cannot use existing settings (checkout, new project) silently fail.
The action should probably report that the settings file is either missing or has no values set.

[Robert Ladyman (saccadic-masking)]

[Notes re: installer]
We have some choices here: the actions requiring the presence of the bzrdefaults file could be disabled if it does not exist (simplest) or the chooser / setup could be run if the file does not exist (and the options always be available).
Alternatively, there could be a setup option (where bzrdefaults does not exist) and then a chooser option once it does exist ('add a repository' or somesuch).

[Robert Ladyman (saccadic-masking)]

Actually, only checkout and new project have a problem. Add and Commit uses the existing .bzr settings.

[Robert Ladyman (saccadic-masking)]

Added (in repochoice series):

sshpass;~/.local/share/nemo/actions/bzrdefaults; to Dependencies section in bzrcheckout.nemo_action and bzrnewproject.nemo_action, so that they do not show as options if the bzrdefaults file does not exist or sshpass has not been installed. (This is for Nemo).

[Robert Ladyman (saccadic-masking)]

Unfortunately, the Dependencies section won't allow relative paths, so ~ cannot be use (/home/username is needed instead). Also, we'd have to modify both the Nemo and Thunar settings: it will be better, I think, to modify the shell scripts to check for a missing bzrdefaults instead.

[Robert Ladyman (saccadic-masking)]

Added checks to runnewproject.sh and runcheckout.sh - this means that the fix now works for Thunar as well.