requirements: add tomli

See comment.

Author: indygreg

requirements.txt

@@ -193,6 +193,10 @@ six==1.16.0 \
     --hash=sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926 \
     --hash=sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254
     # via -r requirements.txt.in
+tomli==2.0.1 \
+    --hash=sha256:939de3e7a6161af0c887ef91b7d41a53e7c5a1ca976325f429cb46ea9bc30ecc \
+    --hash=sha256:de526c12914f0c550d15924c62d72abc48d6fe7364aa87328337a31007fe8a4f
+    # via -r requirements.txt.in
 types-jsonschema==4.17.0.2 \
     --hash=sha256:8b9e1140d4d780f0f19b5cab1b8a3732e8dd5e49dbc1f174cc0b499125ca6f6c \
     --hash=sha256:8fd2f9aea4da54f9a811baa6963aac10fd680c18baa6237392c079b97d152738

requirements.txt.in

@@ -5,6 +5,9 @@ mypy
 PyYAML
 # Undeclared dependency in docker 5.0 package.
 six
+# This is a transitive dependency that doesn't get picked up when running on
+# modern Python. So include to force it in requirements.txt.
+tomli
 types-jsonschema
 types-PyYAML
 zstandard