android-studio-preview: Deprecate the attribute

This also covers "androidStudioPackages.preview".

I believe that the name is confusing (is it from the beta or dev/canary
channel?) and with this error message it should be obvious how to update
ones configuration.

pkgs/applications/editors/android-studio/default.nix

@@ -23,8 +23,15 @@ let
     sha256Hash = "1f7lllj85fia02hgy4ksbqh80sdcml16fv1g892jc6lwykjrdw5y";
   };
 in rec {
-  # Old alias
-  preview = beta;
+  # Old alias (TODO @primeos: Remove after 19.03 is branched off):
+  preview = throw ''
+    The attributes "android-studio-preview" and "androidStudioPackages.preview"
+    are now deprecated and will be removed soon, please use
+    "androidStudioPackages.beta" instead. This attribute corresponds to the
+    beta channel, if you want the latest release you can use
+    "androidStudioPackages.dev" or "androidStudioPackages.canary" instead
+    (currently, there is no difference between both channels).
+  '';
 
   # Attributes are named by their corresponding release channels
 

pkgs/top-level/all-packages.nix

@@ -16053,7 +16053,7 @@ in
   androidStudioPackages = recurseIntoAttrs
     (callPackage ../applications/editors/android-studio { });
   android-studio = androidStudioPackages.stable;
-  android-studio-preview = androidStudioPackages.beta;
+  android-studio-preview = androidStudioPackages.preview;
 
   animbar = callPackage ../applications/graphics/animbar { };