Simplify some exception handling code

Mostly avoid unnecessary usage of sys.exc_info(). Since Python3,
exception objects themselves have all that's needed. They are also
easier to type.

src/_pytest/config/__init__.py

@@ -612,13 +612,9 @@ class PytestPluginManager(PluginManager):
         try:
             __import__(importspec)
         except ImportError as e:
-            new_exc_message = 'Error importing plugin "{}": {}'.format(
-                modname, str(e.args[0])
-            )
-            new_exc = ImportError(new_exc_message)
-            tb = sys.exc_info()[2]
-
-            raise new_exc.with_traceback(tb)
+            raise ImportError(
+                'Error importing plugin "{}": {}'.format(modname, str(e.args[0]))
+            ).with_traceback(e.__traceback__)
 
         except Skipped as e:
             from _pytest.warnings import _issue_warning_captured

src/_pytest/fixtures.py

@@ -862,19 +862,19 @@ class FixtureDef:
         self._finalizers.append(finalizer)
 
     def finish(self, request):
-        exceptions = []
+        exc = None
         try:
             while self._finalizers:
                 try:
                     func = self._finalizers.pop()
                     func()
-                except:  # noqa
-                    exceptions.append(sys.exc_info())
-            if exceptions:
-                _, val, tb = exceptions[0]
-                # Ensure to not keep frame references through traceback.
-                del exceptions
-                raise val.with_traceback(tb)
+                except BaseException as e:
+                    # XXX Only first exception will be seen by user,
+                    #     ideally all should be reported.
+                    if exc is None:
+                        exc = e
+            if exc:
+                raise exc
         finally:
             hook = self._fixturemanager.session.gethookproxy(request.node.fspath)
             hook.pytest_fixture_post_finalizer(fixturedef=self, request=request)

src/_pytest/main.py

@@ -496,11 +496,11 @@ class Session(nodes.FSCollector):
             self.trace.root.indent += 1
             try:
                 yield from self._collect(fspath, parts)
-            except NoMatch:
+            except NoMatch as exc:
                 report_arg = "::".join((str(fspath), *parts))
                 # we are inside a make_report hook so
                 # we cannot directly pass through the exception
-                self._notfound.append((report_arg, sys.exc_info()[1]))
+                self._notfound.append((report_arg, exc))
 
             self.trace.root.indent -= 1
         self._collection_node_cache1.clear()

src/_pytest/python.py

@@ -516,8 +516,7 @@ class Module(nodes.File, PyCollector):
             mod = self.fspath.pyimport(ensuresyspath=importmode)
         except SyntaxError:
             raise self.CollectError(ExceptionInfo.from_current().getrepr(style="short"))
-        except self.fspath.ImportMismatchError:
-            e = sys.exc_info()[1]
+        except self.fspath.ImportMismatchError as e:
             raise self.CollectError(
                 "import file mismatch:\n"
                 "imported module %r has this __file__ attribute:\n"

src/_pytest/runner.py

@@ -133,16 +133,14 @@ def pytest_runtest_call(item):
         pass
     try:
         item.runtest()
-    except Exception:
+    except Exception as e:
         # Store trace info to allow postmortem debugging
-        type, value, tb = sys.exc_info()
-        assert tb is not None
-        tb = tb.tb_next  # Skip *this* frame
-        sys.last_type = type
-        sys.last_value = value
-        sys.last_traceback = tb
-        del type, value, tb  # Get rid of these in this frame
-        raise
+        sys.last_type = type(e)
+        sys.last_value = e
+        assert e.__traceback__ is not None
+        # Skip *this* frame
+        sys.last_traceback = e.__traceback__.tb_next
+        raise e
 
 
 def pytest_runtest_teardown(item, nextitem):
@@ -318,15 +316,13 @@ class SetupState:
             fin = finalizers.pop()
             try:
                 fin()
-            except TEST_OUTCOME:
+            except TEST_OUTCOME as e:
                 # XXX Only first exception will be seen by user,
                 #     ideally all should be reported.
                 if exc is None:
-                    exc = sys.exc_info()
+                    exc = e
         if exc:
-            _, val, tb = exc
-            assert val is not None
-            raise val.with_traceback(tb)
+            raise exc
 
     def _teardown_with_finalization(self, colitem):
         self._callfinalizers(colitem)
@@ -352,15 +348,13 @@ class SetupState:
                 break
             try:
                 self._pop_and_teardown()
-            except TEST_OUTCOME:
+            except TEST_OUTCOME as e:
                 # XXX Only first exception will be seen by user,
                 #     ideally all should be reported.
                 if exc is None:
-                    exc = sys.exc_info()
+                    exc = e
         if exc:
-            _, val, tb = exc
-            assert val is not None
-            raise val.with_traceback(tb)
+            raise exc
 
     def prepare(self, colitem):
         """ setup objects along the collector chain to the test-method
@@ -371,15 +365,15 @@ class SetupState:
         # check if the last collection node has raised an error
         for col in self.stack:
             if hasattr(col, "_prepare_exc"):
-                _, val, tb = col._prepare_exc
-                raise val.with_traceback(tb)
+                exc = col._prepare_exc
+                raise exc
         for col in needed_collectors[len(self.stack) :]:
             self.stack.append(col)
             try:
                 col.setup()
-            except TEST_OUTCOME:
-                col._prepare_exc = sys.exc_info()
-                raise
+            except TEST_OUTCOME as e:
+                col._prepare_exc = e
+                raise e
 
 
 def collect_one_node(collector):