tor: Add torsocks as required package, needed for diagnostics.

Display error for diagnostic if command is missing.

plinth/action_utils.py

@@ -268,6 +268,8 @@ def diagnose_url(url, kind=None, env=None, extra_options=None, wrapper=None,
         # Authorization failed is a success
         if exception.returncode == 6:
             result = 'passed'
+    except FileNotFoundError:
+        result = 'error: missing command'
 
     if kind:
         return [_('Access URL {url} on tcp{kind}')

plinth/modules/tor/tor.py

@@ -55,7 +55,7 @@ def on_install():
     actions.superuser_run('tor', ['setup'])
 
 
-@package.required(['tor', 'obfsproxy'], on_install=on_install)
+@package.required(['tor', 'obfsproxy', 'torsocks'], on_install=on_install)
 def index(request):
     """Service the index page"""
     status = get_status()