Bug 1842916 - Expose WebExtensionInstallException.UserCancelled.

app/src/main/java/org/mozilla/fenix/addons/AddonsManagementFragment.kt

@@ -20,6 +20,7 @@ import androidx.recyclerview.widget.LinearLayoutManager
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Dispatchers.IO
 import kotlinx.coroutines.launch
+import mozilla.components.concept.engine.webextension.WebExtensionInstallException
 import mozilla.components.feature.addons.Addon
 import mozilla.components.feature.addons.AddonManagerException
 import mozilla.components.feature.addons.ui.AddonsManagerAdapter
@@ -219,7 +220,7 @@ class AddonsManagementFragment : Fragment(R.layout.fragment_add_ons_management)
             onError = { _, e ->
                 this@AddonsManagementFragment.view?.let { view ->
                     // No need to display an error message if installation was cancelled by the user.
-                    if (e !is CancellationException) {
+                    if (e !is CancellationException && e !is WebExtensionInstallException.UserCancelled) {
                         val rootView = activity?.getRootView() ?: view
                         context?.let {
                             showSnackBar(