build: Use PYTHON to determine the correct python executable (pydan…

…tic#469)

* build: Use `PYTHON` to determine the correct python executable

* Do not set `PYTHON` in CI

.github/workflows/ci.yml

@@ -77,9 +77,6 @@ jobs:
 
     runs-on: ubuntu-latest
 
-    env:
-      PYTHON: ${{ matrix.python-version }}
-
     steps:
       - uses: actions/checkout@v3
 

build.rs

@@ -1,3 +1,4 @@
+use std::env;
 use std::path::Path;
 use std::process::Command;
 use std::str::from_utf8;
@@ -10,7 +11,7 @@ fn generate_self_schema() {
         // skip running generate_self_schema.py
         return;
     }
-    let output = Command::new("python3")
+    let output = Command::new(env::var("PYTHON").unwrap_or_else(|_| "python3".to_owned()))
         .arg("generate_self_schema.py")
         .output()
         .expect("failed to execute process");