importlib helpers don't provide importlib.thing, but importlib_thing

Fix everywhere.

docs/conf.py

@@ -88,7 +88,7 @@ if on_rtd:
     ]
     sys.modules.update((mod_name, Mock()) for mod_name in MOCK_MODULES)
 
-from importlib.metadata import version as package_version
+from importlib_metadata import version as package_version
 
 # The full version, including alpha/beta/rc tags.
 release = package_version('ocrmypdf').version

setup.cfg

@@ -49,8 +49,8 @@ install_requires =
     cffi>=1.9.1  # must be a setup and install requirement
     coloredlogs>=14.0  # strictly optional
     img2pdf>=0.3.0,<0.5  # pure Python
-    importlib-metadata>=4;python_version<'3.8'
-    importlib-resources>=5;python_version<'3.9'
+    importlib-metadata>=4  # until Python 3.8
+    importlib-resources>=5  # until Python 3.9
     pdfminer.six!=20200720,>=20191110,<=20201018
     pikepdf>=2.10.0
     pikepdf<3;implementation_name=="pypy" and python_version=='3.6'

src/ocrmypdf/_version.py

@@ -5,7 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 
-from importlib.metadata import version as _package_version
+from importlib_metadata import version as _package_version
 
 PROGRAM_NAME = 'ocrmypdf'
 

src/ocrmypdf/pdfa.py

@@ -10,10 +10,10 @@ Utilities for PDF/A production and confirmation with Ghostspcript.
 """
 
 import base64
-import importlib.resources
 from pathlib import Path
 from typing import Dict, Iterator, Union
 
+import importlib_resources
 import pikepdf
 import pkg_resources  # deprecated
 
@@ -104,7 +104,7 @@ def generate_pdfa_ps(target_filename: Path, icc: str = 'sRGB'):
     if icc != 'sRGB':
         raise NotImplementedError("Only supporting sRGB")
 
-    bytes_icc_profile = importlib.resources.read_binary(
+    bytes_icc_profile = importlib_resources.read_binary(
         'ocrmypdf.data', SRGB_ICC_PROFILE_NAME
     )
     ps = '\n'.join(_make_postscript(icc, bytes_icc_profile, 3))