make button labels more consistent

especially back vs cancel

for https://bugs.launchpad.net/subiquity/+bug/1781457

subiquity/ui/views/filesystem/lvm.py

@@ -54,6 +54,11 @@ class VolGroupForm(CompoundDiskForm):
     devices = MultiDeviceField(_("Devices:"))
     size = ReadOnlyField(_("Size:"))
 
+    def validate_devices(self):
+        if len(self.devices.value) < 1:
+            return _("Select at least one device to be part of the volume "
+                     "group.")
+
     def validate_name(self):
         if self.name.value in self.vg_names:
             return _("There is already a volume group named '{}'").format(
@@ -67,6 +72,7 @@ class VolGroupStretchy(Stretchy):
         vg_names = {vg.name for vg in parent.model.all_volgroups()}
         if existing is None:
             title = _('Create LVM volume group')
+            label = _('Create')
             x = 0
             while True:
                 name = 'vg{}'.format(x)
@@ -81,6 +87,7 @@ class VolGroupStretchy(Stretchy):
         else:
             vg_names.remove(existing.name)
             title = _('Edit volume group "{}"').format(existing.name)
+            label = _('Save')
             devices = {d: 'active' for d in existing.devices}
             initial = {
                 'devices': devices,
@@ -93,6 +100,7 @@ class VolGroupStretchy(Stretchy):
 
         form = self.form = VolGroupForm(
             self.parent.model, possible_components, initial, vg_names)
+        self.form.buttons.base_widget[0].set_label(label)
 
         self.form.devices.widget.set_supports_spares(False)
 

subiquity/ui/views/filesystem/raid.py

@@ -95,6 +95,7 @@ class RaidStretchy(Stretchy):
         raid_names = {raid.name for raid in parent.model.all_raids()}
         if existing is None:
             title = _('Create software RAID ("MD") disk')
+            label = _('Create')
             x = 0
             while True:
                 name = 'md{}'.format(x)
@@ -110,6 +111,7 @@ class RaidStretchy(Stretchy):
         else:
             raid_names.remove(existing.name)
             title = _('Edit software RAID disk "{}"').format(existing.name)
+            label = _('Save')
             name = existing.name
             if name.startswith('md/'):
                 name = name[3:]
@@ -131,8 +133,9 @@ class RaidStretchy(Stretchy):
         form = self.form = RaidForm(
             self.parent.model, possible_components, initial, raid_names)
 
-        self.form.devices.widget.set_supports_spares(
+        form.devices.widget.set_supports_spares(
             initial['level'].supports_spares)
+        form.buttons.base_widget[0].set_label(label)
 
         connect_signal(form.level.widget, 'select', self._select_level)
         connect_signal(form.devices.widget, 'change', self._change_devices)

subiquity/ui/views/mirror.py

@@ -36,6 +36,8 @@ mirror_help = _(
 
 class MirrorForm(Form):
 
+    cancel_label = _("Back")
+
     url = URLField(_("Mirror address:"), help=mirror_help)
 
 

subiquity/ui/views/proxy.py

@@ -38,6 +38,8 @@ proxy_help = _("If you need to use a HTTP proxy to access the outside world, "
 
 class ProxyForm(Form):
 
+    cancel_label = _("Back")
+
     url = URLField(_("Proxy address:"), help=proxy_help)
 
 

subiquity/ui/views/snaplist.py

@@ -339,7 +339,7 @@ class SnapListView(BaseView):
                 1: ColSpec(omittable=True),
                 2: ColSpec(pack=False, min_width=40),
                 })
-        ok = ok_btn(label=_("OK"), on_press=self.done)
+        ok = ok_btn(label=_("Done"), on_press=self.done)
         self._main_screen = screen(
             table, [ok],
             focus_buttons=False,

subiquitycore/ui/views/network_configure_manual_interface.py

@@ -245,6 +245,8 @@ class EditNetworkStretchy(Stretchy):
 
 class VlanForm(Form):
 
+    ok_label = _("Create")
+
     def __init__(self, parent, device):
         self.parent = parent
         self.device = device
@@ -425,6 +427,7 @@ class BondStretchy(Stretchy):
             device.name for device in parent.model.get_all_netdevs()}
         if existing is None:
             title = _('Create bond')
+            label = _("Create")
             x = 0
             while True:
                 name = 'bond{}'.format(x)
@@ -437,6 +440,7 @@ class BondStretchy(Stretchy):
                 }
         else:
             title = _('Edit bond')
+            label = _("Save")
             all_netdev_names.remove(existing.name)
             params = existing._configuration['parameters']
             mode = params['mode']
@@ -464,6 +468,7 @@ class BondStretchy(Stretchy):
             if device_ok(device)]
 
         self.form = BondForm(initial, candidate_netdevs, all_netdev_names)
+        self.form.buttons.base_widget[0].set_label(label)
         connect_signal(self.form, 'submit', self.done)
         connect_signal(self.form, 'cancel', self.cancel)
         super().__init__(