fix(msg): use python-oxmsg for MSG email parsing (#3142)

**Summary**
`partition_msg()` previously used the `msg_parser` library for parsing
Outlook MSG email files (.msg files). The `msg_parser` library is
unmaintained and has several major shortcomings such as not being able
to parse MSG files with 8-bit encoded strings and not reliably
extracting attachments.

Use the new and permissively licenced `python-oxmsg` library instead.

**Additional Context**
For reviewability purposes, this PR temporarily places the new
`partition_msg()` implementation in `new_msg.py` and references that
implementation from `msg.py`. `new_msg.py` will be renamed to `msg.py`
in a closely following PR. This avoids a very messy interleaving of
hunks in a diff between the old and re-written `partition_msg()`
implementation.

Fixes #2481 
Fixes #3006

Author: scanny

CHANGELOG.md

@@ -1,13 +1,17 @@
-## 0.14.5-dev1
+## 0.14.5-dev2
 
 ### Enhancements
 
 * **Filtering for tar extraction** Adds tar filtering to the compression module for connectors to avoid decompression malicious content in `.tar.gz` files. This was added to the Python `tarfile` lib in Python 3.12. The change only applies when using Python 3.12 and above.
+* **Use `python-oxmsg` for `partition_msg()`.** Outlook MSG emails are now partitioned using the `python-oxmsg` package which resolves some shortcomings of the prior MSG parser.
 
 ### Features
 
 ### Fixes
 
+* **8-bit string Outlook MSG files are parsed.** `partition_msg()` is now able to parse non-unicode Outlook MSG emails.
+* **Attachments to Outlook MSG files are extracted intact.** `partition_msg()` is now able to extract attachments without corruption.
+
 ## 0.14.4
 
 ### Enhancements

Makefile

@@ -343,7 +343,9 @@ test-extra-markdown:
 
 .PHONY: test-extra-msg
 test-extra-msg:
-	PYTHONPATH=. CI=$(CI) pytest test_unstructured/partition/test_msg.py
+	# NOTE(scanny): exclude attachment test because partitioning attachments requires other extras
+	PYTHONPATH=. CI=$(CI) pytest test_unstructured/partition/test_msg.py \
+          -k "not test_partition_msg_can_process_attachments"
 
 .PHONY: test-extra-odt
 test-extra-odt:

pyproject.toml

@@ -31,6 +31,7 @@ lint.select = [
 ]
 lint.ignore = [
     "COM812",   # -- over aggressively insists on trailing commas where not desireable --
+    "PT001",    # -- wants empty parens on @pytest.fixture where not used (essentially always) --
     "PT005",    # -- flags mock fixtures with names intentionally matching private method name --
     "PT011",    # -- pytest.raises({exc}) too broad, use match param or more specific exception --
     "PT012",    # -- pytest.raises() block should contain a single simple statement --

requirements/extra-msg.in

@@ -1,4 +1,4 @@
 -c ./deps/constraints.txt
 -c base.txt
 
-msg_parser
+python-oxmsg

requirements/extra-msg.txt

@@ -4,7 +4,15 @@
 #
 #    pip-compile ./extra-msg.in
 #
-msg-parser==1.2.0
-    # via -r ./extra-msg.in
+click==8.1.7
+    # via
+    #   -c ./base.txt
+    #   python-oxmsg
 olefile==0.47
-    # via msg-parser
+    # via python-oxmsg
+python-oxmsg==0.0.1
+    # via -r ./extra-msg.in
+typing-extensions==4.12.1
+    # via
+    #   -c ./base.txt
+    #   python-oxmsg