rust: skip initializing curses when TERM isn't set

It relies on it.

Author: indygreg

src/verify_distribution.py

@@ -57,7 +57,10 @@ def error_handler(fif, message):
 
 
 def verify_curses():
-    import curses
+    import curses, os
+
+    if "TERM" not in os.environ:
+        return
 
     curses.initscr()
     curses.endwin()