power: warn if a package manager is running before shutdown/restart

- red colors for warning about running package manager

- red buttons to indicate danger if installation/upgrade runs

plinth/modules/power/templates/power.html

@@ -23,6 +23,15 @@
 
 {% block configuration %}
 
+  {% if pkg_manager_is_busy %}
+    <div class="alert alert-danger">
+    {% blocktrans trimmed %}
+      Currently an installation or upgrade is running.
+      Consider waiting until it's finished before shutting down or restarting.
+    {% endblocktrans %}
+    </div>
+  {% endif %}
+
   <p>
     <a class="btn btn-default btn-md" href="{% url 'power:restart' %}">
       {% trans "Restart &raquo;" %}</a>

plinth/modules/power/templates/power_restart.html

@@ -33,13 +33,28 @@
     {% endblocktrans %}
   </p>
 
+  {% if pkg_manager_is_busy %}
+    <div class="alert alert-danger">
+    {% blocktrans trimmed %}
+      Currently an installation or upgrade is running.
+      Consider waiting until it's finished before restarting.
+    {% endblocktrans %}
+    </div>
+  {% endif %}
+
   <form class="form" method="post">
     {% csrf_token %}
 
     {{ form|bootstrap }}
 
+    {% if pkg_manager_is_busy %}
+      <input type="submit" class="btn btn-danger"
+             value="{% trans "Restart Now" %}"/>
+    {% else %}
       <input type="submit" class="btn btn-primary"
              value="{% trans "Restart Now" %}"/>
+    {% endif %}
+
   </form>
 
 {% endblock %}

plinth/modules/power/templates/power_shutdown.html

@@ -32,13 +32,28 @@
     {% endblocktrans %}
   </p>
 
+  {% if pkg_manager_is_busy %}
+    <div class="alert alert-danger">
+    {% blocktrans trimmed %}
+      Currently an installation or upgrade is running.
+      Consider waiting until it's finished before shutting down.
+    {% endblocktrans %}
+    </div>
+  {% endif %}
+
   <form class="form" method="post">
     {% csrf_token %}
 
     {{ form|bootstrap }}
 
+    {% if pkg_manager_is_busy %}
+      <input type="submit" class="btn btn-danger"
+             value="{% trans "Shut Down Now" %}"/>
+    {% else %}
       <input type="submit" class="btn btn-primary"
              value="{% trans "Shut Down Now" %}"/>
+    {% endif %}
+
   </form>
 
 

plinth/modules/power/views.py

@@ -33,7 +33,8 @@ def index(request):
     """Serve power controls page."""
     return TemplateResponse(request, 'power.html',
                             {'title': power.title,
-                             'description': power.description})
+                             'description': power.description,
+                             'pkg_manager_is_busy': _is_pkg_manager_busy()})
 
 
 def restart(request):
@@ -48,7 +49,8 @@ def restart(request):
 
     return TemplateResponse(request, 'power_restart.html',
                             {'title': _('Power'),
-                             'form': form})
+                             'form': form,
+                             'pkg_manager_is_busy': _is_pkg_manager_busy()})
 
 
 def shutdown(request):
@@ -63,4 +65,14 @@ def shutdown(request):
 
     return TemplateResponse(request, 'power_shutdown.html',
                             {'title': _('Power'),
-                             'form': form})
+                             'form': form,
+                             'pkg_manager_is_busy': _is_pkg_manager_busy()})
+
+
+def _is_pkg_manager_busy():
+    """Return whether a package manager is running."""
+    try:
+        actions.superuser_run('packages', ['is-package-manager-busy'])
+        return True
+    except actions.ActionError:
+        return False