Resolving parts of #688907:

- Replaced bootstrap shell script with Python script. This means
  standalone apps built with bundlebuilder will not work on MacOS < 10.1,
  since we depend (again) on an installed Python.
- Add a hack to set sys.executable; the bootstrap script does os.execve()
  with an argv[0] that's different from the actual Python executable
  (it has to match the CFBundleExecutable entry in the Info.plist to make
  the app work both from the Finder and the command line, and it has to be
  the bootstrap script), yet a proper sys.executable is needed to spawn
  auxiliary processes.

Lib/plat-mac/bundlebuilder.py

@@ -230,7 +230,17 @@ if USE_ZIPIMPORT:
 		path = fullname.replace(".", os.sep) + PYC_EXT
 		return path, MAGIC + '\0\0\0\0' + marshal.dumps(code)
 
+SITECUSTOMIZE_PY = """\
+import sys, os
+executable = os.getenv("PYTHONEXECUTABLE")
+if executable is not None:
+    sys.executable = executable
+"""
+
+SITE_PY += SITECUSTOMIZE_PY
 SITE_CO = compile(SITE_PY, "<-bundlebuilder.py->", "exec")
+SITECUSTOMIZE_CO = compile(SITECUSTOMIZE_PY, "<-bundlebuilder.py->", "exec")
+
 
 EXT_LOADER = """\
 def __load():
@@ -255,15 +265,18 @@ MAYMISS_MODULES = ['mac', 'os2', 'nt', 'ntpath', 'dos', 'dospath',
 STRIP_EXEC = "/usr/bin/strip"
 
 BOOTSTRAP_SCRIPT = """\
-#!/bin/sh
-
-execdir=$(dirname "${0}")
-executable="${execdir}/%(executable)s"
-resdir=$(dirname "${execdir}")/Resources
-main="${resdir}/%(mainprogram)s"
-PYTHONPATH="$resdir"
-export PYTHONPATH
-exec "${executable}" "${main}" "$@"
+#!/usr/bin/env python
+
+import sys, os
+execdir = os.path.dirname(sys.argv[0])
+executable = os.path.join(execdir, "%(executable)s")
+resdir = os.path.join(os.path.dirname(execdir), "Resources")
+mainprogram = os.path.join(resdir, "%(mainprogram)s")
+
+sys.argv.insert(1, mainprogram)
+os.environ["PYTHONPATH"] = resdir
+os.environ["PYTHONEXECUTABLE"] = executable
+os.execve(executable, sys.argv, os.environ)
 """
 
 ARGVEMULATOR="""\
@@ -415,6 +428,10 @@ class AppBuilder(BundleBuilder):
 	def postProcess(self):
 		if self.standalone:
 			self.addPythonModules()
+		else:
+			sitecustomizepath = pathjoin(self.bundlepath, "Contents", "Resources",
+					"sitecustomize" + PYC_EXT)
+			writePyc(SITECUSTOMIZE_CO, sitecustomizepath)
 		if self.strip and not self.symlink:
 			self.stripBinaries()
 
@@ -487,6 +504,9 @@ class AppBuilder(BundleBuilder):
 		site.__code__ = SITE_CO
 		mf.scan_code(SITE_CO, site)
 
+		# warnings.py gets imported implicitly from C
+		mf.import_hook("warnings")
+
 		includeModules = self.includeModules[:]
 		for name in self.includePackages:
 			includeModules.extend(findPackageContents(name).keys())