Warn/fail if /usr/bin/python is called with PYTHON_DISALLOW_AMBIGUOUS_VERSION

See https://fedoraproject.org/wiki/User:Pviktori/Avoid_usr_bin_python_in_RPM_Build

00288-ambiguous-python-version-rpmbuild-warn.patch

@@ -0,0 +1,53 @@
+diff -U3 -r Python-2.7.14.orig/Lib/site.py Python-2.7.14/Lib/site.py
+--- Python-2.7.14.orig/Lib/site.py	2018-01-29 15:05:04.517599815 +0100
++++ Python-2.7.14/Lib/site.py	2018-01-30 09:13:17.305270500 +0100
+@@ -515,6 +515,41 @@
+                 "'import usercustomize' failed; use -v for traceback"
+ 
+ 
++def handle_ambiguous_python_version():
++    """Warn or fail if /usr/bin/python is used
++
++    Behavior depends on the value of PYTHON_DISALLOW_AMBIGUOUS_VERSION:
++    - "warn" - print warning to stderr
++    - "1" - print error and exit with positive exit code
++    - otherwise: do nothing
++
++    This is a Fedora modification, see the Change page for details:
++    See https://fedoraproject.org/wiki/Changes/Avoid_usr_bin_python_in_RPM_Build
++    """
++    if sys.executable == "/usr/bin/python":
++        setting = os.environ.get("PYTHON_DISALLOW_AMBIGUOUS_VERSION")
++        if setting == 'warn':
++            print>>sys.stderr, (
++                "DEPRECATION WARNING: python2 invoked with /usr/bin/python.\n"
++                "    Use /usr/bin/python3 or /usr/bin/python2\n"
++                "    /usr/bin/python will be removed or switched to Python 3"
++                    " in the future.\n"
++                "    If you cannot make the switch now, please follow"
++                    " instructions at"
++                    " https://fedoraproject.org/wiki/Changes/"
++                    "Avoid_usr_bin_python_in_RPM_Build#Quick_Opt-Out")
++        elif setting == '1':
++            print>>sys.stderr, (
++                "ERROR: python2 invoked with /usr/bin/python.\n"
++                "    Use /usr/bin/python3 or /usr/bin/python2\n"
++                "    /usr/bin/python will be switched to Python 3"
++                    " in the future.\n"
++                "    More details are at"
++                    " https://fedoraproject.org/wiki/Changes/"
++                    "Avoid_usr_bin_python_in_RPM_Build#Quick_Opt-Out")
++            exit(1)
++
++
+ def main():
+     global ENABLE_USER_SITE
+ 
+@@ -543,6 +578,7 @@
+     # this module is run as a script, because this code is executed twice.
+     if hasattr(sys, "setdefaultencoding"):
+         del sys.setdefaultencoding
++    handle_ambiguous_python_version()
+ 
+ main()
+ 

python2.spec

@@ -112,7 +112,7 @@ Summary: An interpreted, interactive, object-oriented programming language
 Name: %{python}
 # Remember to also rebase python-docs when changing this:
 Version: 2.7.14
-Release: 8%{?dist}
+Release: 9%{?dist}
 License: Python
 Group: Development/Languages
 Requires: %{python}-libs%{?_isa} = %{version}-%{release}
@@ -758,11 +758,20 @@ Patch285: 00285-fix-non-deterministic-read-in-test_pty.patch
 # Fixed upstream: https://bugs.python.org/issue32186
 Patch287: 00287-fix-thread-hanging-on-inaccessible-nfs-server.patch
 
+# 00288 #
+# Adds a warning when /usr/bin/python is invoked during rpmbuild
+# See https://fedoraproject.org/wiki/User:Pviktori/Avoid_usr_bin_python_in_RPM_Build
+# TODO update the URL in the patch
+# TODO maybe site.py is not a good location for it?
+# TODO update the implementation not to rely on RPM_BUILD_ROOT
+Patch288: 00288-ambiguous-python-version-rpmbuild-warn.patch
+
 # 00289 #
 # Disable automatic detection for the nis module
 # (we handle it it in Setup.dist, see Patch0)
 Patch289: 00289-disable-nis-detection.patch
 
+
 # (New patches go here ^^^)
 #
 # When adding new patches to "python2" and "python3" in Fedora, EL, etc.,
@@ -1086,6 +1095,7 @@ mv Modules/cryptmodule.c Modules/_cryptmodule.c
 %patch284 -p1
 %patch285 -p1
 %patch287 -p1
+%patch288 -p1
 %patch289 -p1
 
 
@@ -1967,6 +1977,10 @@ rm -fr %{buildroot}
 # ======================================================
 
 %changelog
+* Tue Jan 30 2018 Petr Viktorin <pviktori@redhat.com> - 2.7.14-9
+- Add patch 288: warn/fail if Python 2 is called as /usr/bin/python and
+  PYTHON_DISALLOW_AMBIGUOUS_VERSION is set
+
 * Sat Jan 20 2018 Björn Esser <besser82@fedoraproject.org> - 2.7.14-8
 - Rebuilt for switch to libxcrypt