chore(asm): migrate appsec handlers to drop python2 compatibility (#7137

)

drop python 2 and six dependency in `appsec/_handlers.py`

follows #7136

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [ ] Title is accurate.
- [ ] No unnecessary changes are introduced.
- [ ] Description motivates each change.
- [ ] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [ ] Testing strategy adequately addresses listed risk(s).
- [ ] Change is maintainable (easy to change, telemetry, documentation).
- [ ] Release note makes sense to a user of the library.
- [ ] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [ ] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)
- [ ] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [ ] This PR doesn't touch any of that.

ddtrace/appsec/_handlers.py

@@ -1,7 +1,7 @@
 import functools
+import io
 import json
 
-from six import BytesIO
 from wrapt import wrap_function_wrapper as _w
 from wrapt.importer import when_imported
 import xmltodict
@@ -16,12 +16,6 @@
 from ddtrace.internal.logger import get_logger
 
 
-try:
-    from json import JSONDecodeError
-except ImportError:
-    # handling python 2.X import error
-    JSONDecodeError = ValueError  # type: ignore
-
 log = get_logger(__name__)
 _BODY_METHODS = {"POST", "PUT", "DELETE", "PATCH"}
 
@@ -43,7 +37,7 @@ def _on_request_span_modifier(
             if not seekable:
                 content_length = int(environ.get("CONTENT_LENGTH", 0))
                 body = wsgi_input.read(content_length) if content_length else wsgi_input.read()
-                environ["wsgi.input"] = BytesIO(body)
+                environ["wsgi.input"] = io.BytesIO(body)
 
         try:
             if content_type == "application/json" or content_type == "text/json":
@@ -64,7 +58,7 @@ def _on_request_span_modifier(
             RuntimeError,
             TypeError,
             ValueError,
-            JSONDecodeError,
+            json.JSONDecodeError,
             xmltodict.expat.ExpatError,
             xmltodict.ParsingInterrupted,
         ):
@@ -75,7 +69,7 @@ def _on_request_span_modifier(
                 if seekable:
                     wsgi_input.seek(0)
                 else:
-                    environ["wsgi.input"] = BytesIO(body)
+                    environ["wsgi.input"] = io.BytesIO(body)
     return req_body