Catch upcoming deprecations

.github/workflows/scheduled.yml

@@ -33,7 +33,7 @@ jobs:
   # https://twitter.com/alcuadrado/status/1571291687837732873
   update:
     runs-on: ubuntu-latest
-    name: ubuntu / stable / updated
+    name: ubuntu / beta / updated
     # There's no point running this if no Cargo.lock was checked in in the
     # first place, since we'd just redo what happened in the regular test job.
     # Unfortunately, hashFiles only works in if on steps, so we reepeat it.
@@ -42,12 +42,13 @@ jobs:
       - uses: actions/checkout@v3
         with:
           submodules: true
-      - name: Install stable
+      - name: Install beta
         if: hashFiles('Cargo.lock') != ''
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: beta
+          default: true
       - name: cargo update
         if: hashFiles('Cargo.lock') != ''
         uses: actions-rs/cargo@v1
@@ -59,3 +60,5 @@ jobs:
         with:
           command: test
           args: --locked --all-features --all-targets
+        env:
+          RUSTFLAGS: -D deprecated