test: finish fixing the mocks in the pypi_cache

Work towards #3759

tests/pypi/pypi_cache/pypi_cache_tests.bzl

diff --git a/tests/pypi/pypi_cache/pypi_cache_tests.bzl b/tests/pypi/pypi_cache/pypi_cache_tests.bzl
index aa50e1c..c43c65a 100644
--- a/tests/pypi/pypi_cache/pypi_cache_tests.bzl
+++ b/tests/pypi/pypi_cache/pypi_cache_tests.bzl
@@ -270,7 +270,7 @@
 
 def _test_pypi_cache_reads_from_facts_drops_unaccessed_dists(env):
     """Verifies that dists for unaccessed versions are dropped from computed facts."""
-    mock_ctx = mocks.mctx(facts = {
+    mock_ctx = struct(facts = {
         "dist_hashes": {
             "https://{PYPI_INDEX_URL}": {
                 "pkg": {
@@ -363,7 +363,7 @@
 
 def _test_pypi_cache_writes_index_urls_to_facts(env):
     """Verifies that setting index_urls in the cache also populates the facts store."""
-    mock_ctx = mocks.mctx(facts = {})
+    mock_ctx = struct(facts = {})
     cache = _cache(env, mctx = mock_ctx)
 
     fake_result = {
@@ -401,7 +401,7 @@
 
 def _test_pypi_cache_reads_index_urls_from_facts(env):
     """Verifies that reading index_urls from facts works correctly."""
-    mock_ctx = mocks.mctx(facts = {
+    mock_ctx = struct(facts = {
         "fact_version": "v1",
         "index_urls": {
             "https://pypi.org/simple/": {
@@ -432,7 +432,7 @@
 
 def _test_pypi_cache_reads_index_urls_from_facts_incomplete(env):
     """Verifies that incomplete index_urls facts returns None (forces fresh download)."""
-    mock_ctx = mocks.mctx(facts = {
+    mock_ctx = struct(facts = {
         "fact_version": "v1",
         "index_urls": {
             "https://pypi.org/simple/": {
@@ -455,7 +455,7 @@
     appear in computed_facts. This ensures stale facts (from packages
     removed from all requirements files) get cleaned up from the lockfile.
     """
-    mock_ctx = mocks.mctx(facts = {
+    mock_ctx = struct(facts = {
         "fact_version": "v1",
         "index_urls": {
             "https://pypi.org/simple/": {