Remove more libxmp dependencies

docs/conf.py

@@ -74,7 +74,7 @@ if on_rtd:
         def __getattr__(cls, name):
             return MagicMock()
 
-    MOCK_MODULES = ['pikepdf', 'libxmp', 'libxmp.utils', 'ocrmypdf.leptonica']
+    MOCK_MODULES = ['pikepdf', 'ocrmypdf.leptonica']
     sys.modules.update((mod_name, Mock()) for mod_name in MOCK_MODULES)
 
 

src/ocrmypdf/pdfa.py

@@ -32,14 +32,11 @@ Ghostscript's handling of pdfmark.
 """
 
 from binascii import hexlify
-from datetime import datetime
 from pathlib import Path
 from string import Template
 import pkg_resources
 import os
 
-from libxmp.utils import file_to_dict
-from libxmp import consts
 import pikepdf
 
 from pikepdf.models.metadata import (