Print error on readline import failure

Author: jpwoodbu

python/bin/repl_stub.py

@@ -17,32 +17,8 @@
 console_locals = globals().copy()
 
 import code
-import rlcompleter
 import sys
 
-try:
-    import readline
-except ImportError:
-    pass  # readline is not available on all platforms
-
-
-class DynamicCompleter(rlcompleter.Completer):
-    """
-    A custom completer that dynamically updates its namespace to include new
-    imports made within the interactive session.
-    """
-    def __init__(self, namespace):
-        # Store a reference to the namespace, not a copy, so that changes to the namespace are
-        # reflected.
-        self.namespace = namespace
-
-    def complete(self, text, state):
-        # Update the completer's internal namespace with the current interactive session's locals
-        # and globals.  This is the key to making new imports discoverable.
-        rlcompleter.Completer.__init__(self, self.namespace)
-        return super().complete(text, state)
-
-
 if sys.stdin.isatty():
     # Use the default options.
     exitmsg = None
@@ -52,8 +28,27 @@ def complete(self, text, state):
     sys.ps1 = ""
     sys.ps2 = ""
 
-if "readline" in globals():
-    # Set up tab completion.
+# Set up tab completion.
+try:
+    import readline
+    import rlcompleter
+
+    class DynamicCompleter(rlcompleter.Completer):
+        """
+        A custom completer that dynamically updates its namespace to include new
+        imports made within the interactive session.
+        """
+        def __init__(self, namespace):
+            # Store a reference to the namespace, not a copy, so that changes to the namespace are
+            # reflected.
+            self.namespace = namespace
+
+        def complete(self, text, state):
+            # Update the completer's internal namespace with the current interactive session's locals
+            # and globals.  This is the key to making new imports discoverable.
+            rlcompleter.Completer.__init__(self, self.namespace)
+            return super().complete(text, state)
+
     completer = DynamicCompleter(console_locals)
     readline.set_completer(completer.complete)
 
@@ -65,6 +60,8 @@ def complete(self, text, state):
         readline.parse_and_bind("tab: complete")
     else:
         print("Could not enable tab completion!")
+except ImportError:
+    print("Could not enable tab completion!")
 
 # We set the banner to an empty string because the repl_template.py file already prints the banner.
 code.interact(local=console_locals, banner="", exitmsg=exitmsg)