Begin incorporating Python unit tests into build

We now build a separate APE binary for each test so they can run in
parallel. We've got 148 tests running fast and stable so far.

third_party/python/Python/initfsencoding.c

@@ -0,0 +1,107 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=4 sts=4 sw=4 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Python 3                                                                     │
+│ https://docs.python.org/3/license.html                                       │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "third_party/python/Include/codecs.h"
+#include "third_party/python/Include/fileobject.h"
+#include "third_party/python/Include/pyerrors.h"
+#include "third_party/python/Include/pymem.h"
+#include "third_party/python/Include/pystate.h"
+#include "third_party/python/Include/unicodeobject.h"
+#include "third_party/python/Include/yoink.h"
+/* clang-format off */
+
+_Py_IDENTIFIER(name);
+
+static char *
+get_codec_name(const char *encoding)
+{
+    char *name_utf8, *name_str;
+    PyObject *codec, *name = NULL;
+    codec = _PyCodec_Lookup(encoding);
+    if (!codec)
+        goto error;
+    name = _PyObject_GetAttrId(codec, &PyId_name);
+    Py_CLEAR(codec);
+    if (!name)
+        goto error;
+    name_utf8 = PyUnicode_AsUTF8(name);
+    if (name_utf8 == NULL)
+        goto error;
+    name_str = _PyMem_RawStrdup(name_utf8);
+    Py_DECREF(name);
+    if (name_str == NULL) {
+        PyErr_NoMemory();
+        return NULL;
+    }
+    return name_str;
+error:
+    Py_XDECREF(codec);
+    Py_XDECREF(name);
+    return NULL;
+}
+
+static char *
+get_locale_encoding(void)
+{
+#ifdef MS_WINDOWS
+    char codepage[100];
+    PyOS_snprintf(codepage, sizeof(codepage), "cp%d", GetACP());
+    return get_codec_name(codepage);
+#elif defined(__ANDROID__) || defined(__COSMOPOLITAN__)
+    return get_codec_name("UTF-8");
+#elif defined(HAVE_LANGINFO_H) && defined(CODESET)
+    char* codeset = nl_langinfo(CODESET);
+    if (!codeset || codeset[0] == '\0') {
+        PyErr_SetString(PyExc_ValueError, "CODESET is not set or empty");
+        return NULL;
+    }
+    return get_codec_name(codeset);
+#else
+    PyErr_SetNone(PyExc_NotImplementedError);
+    return NULL;
+#endif
+}
+
+int
+_Py_InitFsEncoding(PyInterpreterState *interp)
+{
+    PyObject *codec;
+
+#ifdef MS_WINDOWS
+    if (Py_LegacyWindowsFSEncodingFlag)
+    {
+        Py_FileSystemDefaultEncoding = "mbcs";
+        Py_FileSystemDefaultEncodeErrors = "replace";
+    }
+    else
+    {
+        Py_FileSystemDefaultEncoding = "utf-8";
+        Py_FileSystemDefaultEncodeErrors = "surrogatepass";
+    }
+#else
+    if (Py_FileSystemDefaultEncoding == NULL)
+    {
+        Py_FileSystemDefaultEncoding = get_locale_encoding();
+        if (Py_FileSystemDefaultEncoding == NULL)
+            Py_FatalError("Py_Initialize: Unable to get the locale encoding");
+        Py_HasFileSystemDefaultEncoding = 0;
+        interp->fscodec_initialized = 1;
+        return 0;
+    }
+#endif
+
+    /* the encoding is mbcs, utf-8 or ascii */
+    codec = _PyCodec_Lookup(Py_FileSystemDefaultEncoding);
+    if (!codec) {
+        /* Such error can only occurs in critical situations: no more
+         * memory, import a module of the standard library failed,
+         * etc. */
+        return -1;
+    }
+    Py_DECREF(codec);
+    interp->fscodec_initialized = 1;
+    return 0;
+}