Do not run yay if Python is not the system Python (fixes #13)

src/linux.rs

@@ -19,6 +19,10 @@ pub enum Distribution {
 #[fail(display = "Unknown Linux Distribution")]
 struct UnknownLinuxDistribution;
 
+#[derive(Debug, Fail)]
+#[fail(display = "Detected Python is not the system Python")]
+struct NotSystemPython;
+
 impl Distribution {
     pub fn detect() -> Result<Self, failure::Error> {
         let content = fs::read_to_string("/etc/os-release")?;
@@ -52,6 +56,17 @@ pub fn upgrade_arch_linux(
     terminal: &Terminal,
 ) -> Result<(), failure::Error> {
     if let Ok(yay) = which("yay") {
+        if let Ok(python) = which("python") {
+            if python != PathBuf::from("/usr/bin/python") {
+                terminal.print_warning(format!(
+                    "Python detected at {:?}, which is probably not the system Python.
+It's dangerous to run yay since Python based AUR packages will be installed in the wrong location",
+                    python
+                ));
+                return Err(NotSystemPython.into());
+            }
+        }
+
         Command::new(yay).spawn()?.wait()?.check()?;
     } else {
         if let Some(sudo) = &sudo {