MAINT: refer to python3 in refguide_check (scipy#16937)

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Co-authored-by: Ralf Gommers <ralf.gommers@gmail.com>

Author: perimosocordiae

dev.py

@@ -1006,7 +1006,9 @@ def task_meta(cls, **kwargs):
         args = Args(**kwargs)
         dirs = Dirs(args)
 
-        cmd = [str(dirs.root / 'tools' / 'refguide_check.py'), '--doctests']
+        cmd = [f'{sys.executable}',
+               str(dirs.root / 'tools' / 'refguide_check.py'),
+               '--doctests']
         if args.verbose:
             cmd += ['-vvv']
         if args.submodule:

tools/refguide_check.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
 refguide_check.py [OPTIONS] [-- ARGS]
 
@@ -7,7 +7,7 @@
 
 Example of usage::
 
-    $ python refguide_check.py optimize
+    $ python3 refguide_check.py optimize
 
 Note that this is a helper script to be able to check if things are missing;
 the output of this script does need to be checked manually.  In some cases
@@ -19,7 +19,7 @@
 scipy docstrings doctestable!], this is just to make sure that code in
 docstrings is valid python::
 
-    $ python refguide_check.py --doctests optimize
+    $ python3 refguide_check.py --doctests optimize
 
 """
 import copy