CI: Remove faulthandler fallback requirement

faulthandler is a stdlib module in Python 3.3+. For a long time a PyPI package
of the same name was available for earlier Python releases. That package has
since been removed from PyPI, and the source respoitory archived. So we should
not rely on it.
fixes #983 refs #970

docs/ansible_detailed.rst

@@ -1248,18 +1248,17 @@ with ``-vvv``.
 
 However, certain controller hangs may render ``MITOGEN_DUMP_THREAD_STACKS``
 ineffective, or occur too infrequently for interactive reproduction. In these
-cases `faulthandler <https://faulthandler.readthedocs.io/>`_ may be used:
+cases :py:mod:`faulthandler` may be used with Python >= 3.3:
 
-1. For Python 2, ``pip install faulthandler``. This is unnecessary on Python 3.
-2. Once the hang occurs, observe the process tree using ``pstree`` or ``ps
+1. Once the hang occurs, observe the process tree using ``pstree`` or ``ps
    --forest``.
-3. The most likely process to be hung is the connection multiplexer, which can
+2. The most likely process to be hung is the connection multiplexer, which can
    easily be identified as the parent of all SSH client processes.
-4. Send ``kill -SEGV <pid>`` to the multiplexer PID, causing it to print all
+3. Send ``kill -SEGV <pid>`` to the multiplexer PID, causing it to print all
    thread stacks.
-5. `File a bug <https://github.com/dw/mitogen/issues/new/>`_ including a copy
-   of the stacks, along with a description of the last task executing prior to
-   the hang.
+4. `File a bug <https://github.com/mitogen-hq/mitogen/issues/new/>`_
+   including a copy of the stacks and a description of the last task executing
+   before the hang
 
 It is possible the hang occurred in a process on a target. If ``strace`` is
 available, look for the host name not listed in Ansible output as reporting a

docs/changelog.rst

@@ -27,6 +27,7 @@ v0.3.4.dev0
   was made to enqueue a message with a Broker that has already exitted`. However it may result in
   resource leaks.
 * :gh:issue:`659` Removed :mod:`mitogen.compat.simplejson`, not needed with Python 2.7+, contained Python 3.x syntax errors
+* :gh:issue:`983` CI: Removed PyPI faulthandler requirement from tests
 
 v0.3.3 (2022-06-03)
 -------------------

tests/requirements.txt

@@ -2,7 +2,6 @@ psutil==5.4.8
 coverage==5.5;      python_version < '3.7'
 coverage==6.4.4;    python_version >= '3.7'
 Django==1.6.11  # Last version supporting 2.6.
-faulthandler==3.2; python_version < '3.3'
 mock==2.0.0
 pytz==2018.5
 cffi==1.14.3  # Random pin to try and fix pyparser==2.18 not having effect