gh-116303: Handle disabled test modules in test.support

Lib/test/support/__init__.py

@@ -1715,7 +1715,10 @@ def run_in_subinterp(code):
     module is enabled.
     """
     _check_tracemalloc()
-    import _testcapi
+    try:
+        import _testcapi
+    except ImportError:
+        raise unittest.SkipTest("requires _testcapi")
     return _testcapi.run_in_subinterp(code)
 
 
@@ -1725,7 +1728,10 @@ def run_in_subinterp_with_config(code, *, own_gil=None, **config):
     module is enabled.
     """
     _check_tracemalloc()
-    import _testinternalcapi
+    try:
+        import _testinternalcapi
+    except ImportError:
+        raise unittest.SkipTest("requires _testinternalcapi")
     if own_gil is not None:
         assert 'gil' not in config, (own_gil, config)
         config['gil'] = 2 if own_gil else 1
@@ -1887,13 +1893,12 @@ def restore(self):
 
 
 def with_pymalloc():
-    import _testcapi
-    return _testcapi.WITH_PYMALLOC and not Py_GIL_DISABLED
+    WITH_PYMALLOC = bool(sysconfig.get_config_var("WITH_PYMALLOC"))
+    return WITH_PYMALLOC and not Py_GIL_DISABLED
 
 
 def with_mimalloc():
-    import _testcapi
-    return _testcapi.WITH_MIMALLOC
+    return bool(sysconfig.get_config_var("WITH_MIMALLOC"))
 
 
 class _ALWAYS_EQ:

Lib/test/support/bytecode_helper.py

@@ -3,7 +3,7 @@
 import unittest
 import dis
 import io
-from _testinternalcapi import compiler_codegen, optimize_cfg, assemble_code_object
+from test.support import import_helper
 
 _UNSPECIFIED = object()
 
@@ -136,20 +136,23 @@ def complete_insts_info(self, insts):
 class CodegenTestCase(CompilationStepTestCase):
 
     def generate_code(self, ast):
-        insts, _ = compiler_codegen(ast, "my_file.py", 0)
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
+        insts, _ = _testinternalcapi.compiler_codegen(ast, "my_file.py", 0)
         return insts
 
 
 class CfgOptimizationTestCase(CompilationStepTestCase):
 
     def get_optimized(self, insts, consts, nlocals=0):
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
         insts = self.normalize_insts(insts)
         insts = self.complete_insts_info(insts)
-        insts = optimize_cfg(insts, consts, nlocals)
+        insts = _testinternalcapi.optimize_cfg(insts, consts, nlocals)
         return insts, consts
 
 class AssemblerTestCase(CompilationStepTestCase):
 
     def get_code_object(self, filename, insts, metadata):
-        co = assemble_code_object(filename, insts, metadata)
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
+        co = _testinternalcapi.assemble_code_object(filename, insts, metadata)
         return co