Update nightly for unused_braces regression

https://github.com/rust-lang/rust/issues/70814
diff --git a/.travis.yml b/.travis.yml
index a5a766b..ea37022 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -82,7 +82,7 @@
   allow_failures:
     - rust: nightly
   include:
-  - rust: nightly-2020-04-23
+  - rust: nightly-2020-05-01
     name: "Compile tests"
     env: RUSTFLAGS="--cap-lints=warn"
     script:
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 1952595..0185f04 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -167,7 +167,7 @@
     - template: _build/install-rust.yml
       parameters:
         platform: Linux
-        rust_version: nightly-2020-04-23
+        rust_version: nightly-2020-05-01
     - bash: |
         sudo apt-get update &&
         sudo apt-get -y install libsqlite3-dev libpq-dev libmysqlclient-dev
diff --git a/diesel_compile_tests/rust-toolchain b/diesel_compile_tests/rust-toolchain
index 49343ab..1bc2439 100644
--- a/diesel_compile_tests/rust-toolchain
+++ b/diesel_compile_tests/rust-toolchain
@@ -1 +1 @@
-nightly-2020-04-23
+nightly-2020-05-01