[feat] Omit Python library in script paths

This is useful when using OS Python & eggs.

Useless for SlapOS.

src/zc/buildout/easy_install.py

@@ -20,6 +20,7 @@ installed.
 
 import copy
 import distutils.errors
+import distutils.sysconfig
 import errno
 import glob
 import logging
@@ -101,6 +102,8 @@ pip_path = setuptools_path = [
   ]
 pip_pythonpath = setuptools_pythonpath = os.pathsep.join(pip_path)
 
+python_lib = distutils.sysconfig.get_python_lib()
+
 FILE_SCHEME = re.compile('file://', re.I).match
 DUNDER_FILE_PATTERN = re.compile(r"__file__ = '(?P<filename>.+)'$")
 
@@ -1162,6 +1165,10 @@ def scripts(reqs, working_set, executable, dest=None,
         if p not in unique_path:
             unique_path.append(p)
     path = [realpath(p) for p in unique_path]
+    try:
+        path.remove(python_lib)
+    except ValueError:
+        pass
 
     generated = []
 
@@ -1332,6 +1339,12 @@ join = os.path.join
 base = os.path.dirname(os.path.abspath(os.path.realpath(__file__)))
 """
 
+def _initialization(path, initialization):
+    return """sys.path[0:0] = [
+  %s,
+  ]
+""" % path + initialization if path else initialization
+
 def _script(module_name, attrs, path, dest, arguments, initialization, rsetup):
     if is_win32:
         dest += '-script.py'
@@ -1340,11 +1353,10 @@ def _script(module_name, attrs, path, dest, arguments, initialization, rsetup):
 
     contents = script_template % dict(
         python = python,
-        path = path,
         module_name = module_name,
         attrs = attrs,
         arguments = arguments,
-        initialization = initialization,
+        initialization = _initialization(path, initialization),
         relative_paths_setup = rsetup,
         )
     return _create_script(contents, dest)
@@ -1377,8 +1389,7 @@ def _distutils_script(path, dest, script_content, initialization, rsetup):
 
     contents = distutils_script_template % dict(
         python = python,
-        path = path,
-        initialization = initialization,
+        initialization = _initialization(path, initialization),
         relative_paths_setup = rsetup,
         before = before,
         after = after
@@ -1446,9 +1457,6 @@ script_template = script_header + '''\
 
 %(relative_paths_setup)s
 import sys
-sys.path[0:0] = [
-  %(path)s,
-  ]
 %(initialization)s
 import %(module_name)s
 
@@ -1460,9 +1468,6 @@ distutils_script_template = script_header + '''
 %(before)s
 %(relative_paths_setup)s
 import sys
-sys.path[0:0] = [
-  %(path)s,
-  ]
 %(initialization)s
 
 %(after)s'''
@@ -1475,14 +1480,12 @@ def _pyscript(path, dest, rsetup, initialization=''):
         dest += '-script.py'
 
     python = _safe_arg(sys.executable)
-    if path:
-        path += ','  # Courtesy comma at the end of the list.
 
     contents = py_script_template % dict(
         python = python,
         path = path,
         relative_paths_setup = rsetup,
-        initialization=initialization,
+        initialization = _initialization(path, initialization),
         )
     changed = _file_changed(dest, contents)
 
@@ -1517,9 +1520,6 @@ py_script_template = script_header + '''\
 %%(relative_paths_setup)s
 import sys
 
-sys.path[0:0] = [
-  %%(path)s
-  ]
 %%(initialization)s
 
 _interactive = True

src/zc/buildout/tests/easy_install.txt

@@ -765,9 +765,9 @@ An interpreter can also be generated without other eggs:
     <BLANKLINE>
     import sys
     <BLANKLINE>
-    sys.path[0:0] = [
     <BLANKLINE>
-      ]
+    <BLANKLINE>
+    _interactive = True
     ...
 
 An additional argument can be passed to define which scripts to install