Ensure that python scripts executed during the build use the same python
interpreter specified as $PYTHON by the spec file.

https://bugzilla.redhat.com/show_bug.cgi?id=1552079

--- subversion-1.9.7/build/generator/gen_make.py.pybinary
+++ subversion-1.9.7/build/generator/gen_make.py
@@ -507,7 +507,7 @@
     standalone.write('top_srcdir = .\n')
     standalone.write('top_builddir = .\n')
     standalone.write('SWIG = swig\n')
-    standalone.write('PYTHON = python\n')
+    standalone.write('PYTHON = ' + sys.executable + '\n')
     standalone.write('\n')
     standalone.write(open("build-outputs.mk","r").read())
     standalone.close()
--- subversion-1.9.7/subversion/tests/cmdline/svntest/main.py.pybinary
+++ subversion-1.9.7/subversion/tests/cmdline/svntest/main.py
@@ -410,9 +410,9 @@
   should be passed to wait_on_pipe."""
   command = [str(x) for x in command]
 
-  # On Windows subprocess.Popen() won't accept a Python script as
-  # a valid program to execute, rather it wants the Python executable.
-  if (sys.platform == 'win32') and (command[0].endswith('.py')):
+  # Always run python scripts under the same Python executable as used
+  # for the test suite.
+  if command[0].endswith('.py'):
     command.insert(0, sys.executable)
 
   command_string = command[0] + ' ' + ' '.join(map(_quote_arg, command[1:]))