Add 'launch' hook, based on pip.utils.setuptools_build

CHANGES.txt

@@ -2,6 +2,21 @@
 CHANGES
 =======
 
+19.6
+----
+
+* Added a new entry script ``setuptools.launch``,
+  implementing the shim found in
+  ``pip.util.setuptools_build``. Use this command to launch
+  distutils-only packages under setuptools in the same way that
+  pip does, causing the setuptools monkeypatching of distutils
+  to be invoked prior to invoking a script. Useful for debugging
+  or otherwise installing a distutils-only package under
+  setuptools when pip isn't available or otherwise does not
+  expose the desired functionality. For example::
+
+    $ python -m setuptools.launch setup.py develop
+
 19.5
 ----
 

setuptools/launch.py

+"""
+Launch the Python script on the command line after
+setuptools is bootstrapped via import.
+"""
+
+# Note that setuptools gets imported implicitly by the
+# invocation of this script using python -m setuptools.launch
+
+import tokenize
+import sys
+
+
+def load():
+	"""
+	Load the script in sys.argv[1] and run it as if it had
+	been invoked naturally.
+	"""
+	globals()['__file__'] = sys.argv[1]
+	sys.argv[:] = sys.argv[1:]
+
+	open_ = getattr(tokenize, 'open', open)
+	script = open_(__file__).read()
+	norm_script = script.replace('\\r\\n', '\\n')
+	return compile(norm_script, __file__, 'exec')
+
+
+if __name__ == '__main__':
+	exec(load())