Don't test features to implement --hide=all

Previously, using `--hide=all` or `--hide=optional` would result in
features being tested, including external ones, in particular internet.

Those are not supposed to be tested, for instance when running
`--optional=all` they won't be tested.

The current commit makes unnecessary to test any feature for
implementing the `--hide` option.

Author: Matthias Koeppe

src/sage/doctest/control.py

@@ -1502,18 +1502,14 @@ def run(self):
             available_software._allow_external = self.options.optional is True or 'external' in self.options.optional
 
             for h in self.options.hide:
-                try:
+                if h in available_software:
                     i = available_software._indices[h]
-                except KeyError:
-                    pass
-                else:
                     f = available_software._features[i]
-                    if f.is_present():
-                        f.hide()
-                        self.options.hidden_features.add(f)
-                        for g in f.joined_features():
-                            if g.name in self.options.optional:
-                                self.options.optional.discard(g.name)
+                    f.hide()
+                    self.options.hidden_features.add(f)
+                    for g in f.joined_features():
+                        if g.name in self.options.optional:
+                            self.options.optional.discard(g.name)
 
             for o in self.options.disabled_optional:
                 try: