feat(python): display warning message when trying to use an unsupport…

…ed Python version

Closes astral-sh#2587.

crates/uv/src/commands/venv.rs

@@ -23,6 +23,7 @@ use uv_resolver::{InMemoryIndex, OptionsBuilder};
 use uv_types::{
     BuildContext, BuildIsolation, ConfigSettings, InFlight, NoBinary, NoBuild, SetupPyStrategy,
 };
+use uv_warnings::warn_user;
 
 use crate::commands::ExitStatus;
 use crate::printer::Printer;
@@ -113,6 +114,10 @@ async fn venv_impl(
         find_default_python(cache).into_diagnostic()?
     };
 
+    if interpreter.python_tuple() < (3, 8) {
+        warn_user!("uv is not officially compatible with Python 3.7 or lower")
+    }
+
     writeln!(
         printer.stderr(),
         "Using Python {} interpreter at: {}",