00251: Change user install location

Set values of prefix and exec_prefix in distutils install command
to /usr/local if executable is /usr/bin/python* and RPM build
is not detected to make pip and distutils install into separate location.

Fedora Change: https://fedoraproject.org/wiki/Changes/Making_sudo_pip_safe
Downstream only: Awaiting resources to work on upstream PEP

Author: mcyprian

Lib/distutils/command/install.py

@@ -419,8 +419,19 @@ def finalize_unix(self):
                     raise DistutilsOptionError(
                           "must not supply exec-prefix without prefix")
 
-                self.prefix = os.path.normpath(sys.prefix)
-                self.exec_prefix = os.path.normpath(sys.exec_prefix)
+                # self.prefix is set to sys.prefix + /local/
+                # if neither RPM build nor virtual environment is
+                # detected to make pip and distutils install packages
+                # into the separate location.
+                if (not (hasattr(sys, 'real_prefix') or
+                    sys.prefix != sys.base_prefix) and
+                    'RPM_BUILD_ROOT' not in os.environ):
+                    addition = "/local"
+                else:
+                    addition = ""
+
+                self.prefix = os.path.normpath(sys.prefix) + addition
+                self.exec_prefix = os.path.normpath(sys.exec_prefix) + addition
 
             else:
                 if self.exec_prefix is None:

Lib/site.py

@@ -353,7 +353,14 @@ def getsitepackages(prefixes=None):
     return sitepackages
 
 def addsitepackages(known_paths, prefixes=None):
-    """Add site-packages to sys.path"""
+    """Add site-packages to sys.path
+
+    '/usr/local' is included in PREFIXES if RPM build is not detected
+    to make packages installed into this location visible.
+
+    """
+    if ENABLE_USER_SITE and 'RPM_BUILD_ROOT' not in os.environ:
+        PREFIXES.insert(0, "/usr/local")
     for sitedir in getsitepackages(prefixes):
         if os.path.isdir(sitedir):
             addsitedir(sitedir, known_paths)