Fix path search upon python3 -m maturin

maturin/__main__.py

@@ -2,8 +2,41 @@
 import sys
 from pathlib import Path
 import sysconfig
+from typing import Optional
+
+
+def get_maturin_path() -> Optional[Path]:
+    SCRIPT_NAME = "maturin"
+
+    def script_dir(scheme: str) -> Path:
+        return sysconfig.get_path("scripts", scheme)
+
+    def script_exists(dir: Path) -> bool:
+        for _, _, files in os.walk(dir):
+            for f in files:
+                name, *_ = os.path.splitext(f)
+                if name == SCRIPT_NAME:
+                    return True
+
+        return False
+
+    paths = list(
+        filter(
+            script_exists,
+            filter(os.path.exists, map(script_dir, sysconfig.get_scheme_names())),
+        )
+    )
+
+    if paths:
+        return Path(paths[0]) / SCRIPT_NAME
+
+    return None
+
 
 if __name__ == "__main__":
-    scripts_dir = sysconfig.get_path("scripts")
-    maturin = Path(scripts_dir) / "maturin"
+    maturin = get_maturin_path()
+    if maturin is None:
+        print("Unable to find `maturin` script")
+        exit(1)
+
     os.execv(maturin, [str(maturin)] + sys.argv[1:])