TW-1734: calendar gives an error when context is set

- Thanks to Simon Michael.

ChangeLog

@@ -31,6 +31,7 @@
 - TW-1729 zsh completion: zregexparse:4: not enough regex argument (thanks to
           Daniel Shahaf).
 - TW-1733 taskwarrior 2.5.0 can not compile FreeBSD 10.1 (thanks to ribbon).
+- TW-1734 calendar gives an error when context is set (thanks to Simon Michael).
 - TW-1735 context with no subcommand should do something (thanks to Simon
           Michael).
 - TW-1736 Error on detection of BOM in files.

src/commands/CmdCalendar.cpp

@@ -49,7 +49,7 @@ CmdCalendar::CmdCalendar ()
   _read_only             = true;
   _displays_id           = true;
   _needs_gc              = true;
-  _uses_context          = true;
+  _uses_context          = false;
   _accepts_filter        = false;
   _accepts_modifications = false;
   _accepts_miscellaneous = true;

test/context.t

@@ -534,6 +534,17 @@ class ContextErrorHandling(TestCase):
         code, out, err = self.t("context show")
         self.assertIn("No context is currently applied.", out)
 
+class TestBug1734(TestCase):
+    def setUp(self):
+        self.t = Task()
+        self.t("add zero")
+        self.t("add one +tag")
+        self.t("context define foo +tag", input="y\n")
+
+    def test_calendar(self):
+        """The 'calendar' command should not fail when a context is active"""
+        code, out, err = self.t("calendar")
+
 
 # TODO Prove context does not interfere with export
 # TODO Prove context does not interfere with undo