Remove test_exit_crash.py

This file contains two tests, one of which has been skipped forever,
and the second (test_pg_exit) has been a flakey test that does not test
in general, testing a use-case we likely do not see any more.  So
therefore I am removing this test from the library.

tests/test_exit_crash.py

@@ -1,79 +0,0 @@
-# -*- coding: utf-8 -*-
-import os
-import sys
-import subprocess
-import tempfile
-import pyqtgraph as pg
-import pytest
-import textwrap
-import time
-
-code = """
-import sys
-sys.path.insert(0, '{path}')
-import pyqtgraph as pg
-app = pg.mkQApp()
-w = pg.{classname}({args})
-"""
-
-skipmessage = ('unclear why this test is failing. skipping until someone has'
-               ' time to fix it')
-
-
-def call_with_timeout(*args, **kwargs):
-    """Mimic subprocess.call with timeout for python < 3.3"""
-    wait_per_poll = 0.1
-    try:
-        timeout = kwargs.pop('timeout')
-    except KeyError:
-        timeout = 10
-
-    rc = None
-    p = subprocess.Popen(*args, **kwargs)
-    for i in range(int(timeout/wait_per_poll)):
-        rc = p.poll()
-        if rc is not None:
-            break
-        time.sleep(wait_per_poll)
-    return rc
-
-
-@pytest.mark.skipif(True, reason=skipmessage)
-def test_exit_crash():
-    # For each Widget subclass, run a simple python script that creates an
-    # instance and then shuts down. The intent is to check for segmentation
-    # faults when each script exits.
-    tmp = tempfile.mktemp(".py")
-    path = os.path.dirname(pg.__file__)
-
-    initArgs = {
-        'CheckTable': "[]",
-        'ProgressDialog': '"msg"',
-        'VerticalLabel': '"msg"',
-    }
-
-    for name in dir(pg):
-        obj = getattr(pg, name)
-        if not isinstance(obj, type) or not issubclass(obj, pg.QtGui.QWidget):
-            continue
-
-        print(name)
-        argstr = initArgs.get(name, "")
-        with open(tmp, 'w') as f:
-            f.write(code.format(path=path, classname=name, args=argstr))
-        proc = subprocess.Popen([sys.executable, tmp])
-        assert proc.wait() == 0
-
-    os.remove(tmp)
-
-@pytest.mark.skipif(pg.Qt.QtVersion.startswith("5.9"), reason="Functionality not well supported, failing only on this config")
-def test_pg_exit():
-    # test the pg.exit() function
-    code = textwrap.dedent("""
-        import pyqtgraph as pg
-        app = pg.mkQApp()
-        pg.plot()
-        pg.exit()
-    """)
-    rc = call_with_timeout([sys.executable, '-c', code], timeout=5, shell=False)
-    assert rc == 0