Migrate to 2021 edition

Author: coolreader18

Cargo.toml

@@ -5,7 +5,7 @@ description = "Compiler for python code into bytecode for the rustpython VM."
 authors = ["RustPython Team"]
 repository = "https://github.com/RustPython/RustPython"
 license = "MIT"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 indexmap = "1.0"

porcelain/Cargo.toml

@@ -3,7 +3,7 @@ name = "rustpython-compiler"
 version = "0.1.2"
 description = "A usability wrapper around rustpython-parser and rustpython-compiler-core"
 authors = ["RustPython Team"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 thiserror = "1.0"