remove auto-sys-last-traceback functionality

Author: Christopher Rowley

CHANGELOG.md

@@ -6,6 +6,8 @@
   * Comparisons like `==`, `<` and `isless` between `Py`s now return `Bool` instead of `Py`.
   * Removed comparisons between `Py` and `Number` (like `Py(3) < 5`).
   * Removed arithmetic between `Py` and `Number` (like `Py(2) * 10`).
+  * Python errors no longer automatically set `sys.last_traceback` etc. when displayed from Julia.
+  * Removed `CONFIG.auto_sys_last_traceback`.
 * Changes to `PythonCall.GC` (now more like `Base.GC`):
   * `enable(true)` replaces `enable()`.
   * `enable(false)` replaces `disable()`.

docs/src/compat.md

@@ -5,10 +5,6 @@ Some packages require a little extra help to work nicely with PythonCall.
 Some of these are "fixes" that are silently applied for you, and some are just extra
 functions to bridge a gap. We aim to keep these as minimal as possible.
 
-## Python standard library
-
-Whenever a Python exception is displayed by Julia, `sys.last_traceback` and friends are set. This allows the post-mortem debugger `pdb.pm()` to work. Disable by setting `PythonCall.CONFIG.auto_sys_last_traceback = false`.
-
 ## Julia standard library
 
 Python objects can be serialised with the [`Serialization`](https://docs.julialang.org/en/v1/stdlib/Serialization/) stdlib.

docs/src/faq.md

@@ -116,3 +116,9 @@ Each release of PythonCall and JuliaCall will support and require:
 - The current Julia LTS version and newer, [see here](https://julialang.org/downloads/#long_term_support_release). Currently 1.10+.
 
 Only the latest patch release within each minor version is supported.
+
+## Can I use the Python debugger `pdb` from Julia?
+
+Yes! If you are used to using the post-mortem debugger `pdb.pm()` in Python, then you
+can instead use `pdb.post_mortem(err[1].exception)` at the Julia REPL to debug the
+most recent Python error (a [`PyException`](@ref)).

docs/src/v1-migration-guide.md

@@ -24,6 +24,12 @@ between Python and Julia is explicit.
 * Instead of `Py(5) * 6` use `Py(5) * Py(6)` or `pymul(Py(5), 6)`.
 * Instead of `np.array([1,2,3]) < 3` use `pylt(np.array([1,2,3]), 3)`.
 
+When a Python error is displayed in Julia, PythonCall no longer sets `sys.last_traceback`
+and friends. This means that the Python post-mortem debugger `pdb.pm()` will no longer
+work.
+
+* Instead of `pdb.pm()` use `pdb.post_mortem(err[1].exception)`.
+
 ## `PythonCall.GC`
 
 This submodule has been changed to closer mimic the `Base.GC` API.

src/Core/config.jl

@@ -1,6 +1,5 @@
 @kwdef mutable struct Config
     meta::String = ""
-    auto_sys_last_traceback::Bool = true
     auto_fix_qt_plugin_path::Bool = true
 end
 

src/Core/err.jl

@@ -105,17 +105,6 @@ function _showerror(io::IO, e::PyException, bt; backtrace = true)
         return
     end
 
-    if CONFIG.auto_sys_last_traceback
-        try
-            sys = pyimport("sys")
-            sys.last_type = e.t
-            sys.last_value = e.v
-            sys.last_traceback = e.b
-        catch err
-            print(io, "<error while setting 'sys.last_traceback': $err>")
-        end
-    end
-
     if !pyisnull(pyJuliaError) && pyissubclass(e.t, pyJuliaError)
         # handle Julia exceptions specially
         try