debugger: load 'ipdb' if present

Transparently chooses between the IPython-enhanced 'ipdb' or the
standard 'pdb'.

datasette/handle_exception.py

@@ -5,9 +5,13 @@
 )
 from .views.base import DatasetteError
 from markupsafe import Markup
-import pdb
 import traceback
 
+try:
+    import ipdb as pdb
+except ImportError:
+    import pdb
+
 try:
     import rich
 except ImportError:

docs/contributing.rst

@@ -111,7 +111,7 @@ Debugging
 
 Any errors that occur while Datasette is running while display a stack trace on the console.
 
-You can tell Datasette to open an interactive ``pdb`` debugger session if an error occurs using the ``--pdb`` option::
+You can tell Datasette to open an interactive ``pdb`` (or ``ipdb``, if present) debugger session if an error occurs using the ``--pdb`` option::
 
     datasette --pdb fixtures.db
 
@@ -345,4 +345,4 @@ Datasette bundles `CodeMirror <https://codemirror.net/>`__ for the SQL editing i
       -p @rollup/plugin-node-resolve \
       -p @rollup/plugin-terser
 
-* Update the version reference in the ``codemirror.html`` template.
+* Update the version reference in the ``codemirror.html`` template.