Move all python shebangs from /usr/bin/env to python3.

The change is only relevant to development as all the call to python scripts is done
calling C++ os::python that invoques the appropriate python version.

The change is two fold, on one hand remove all the uses of /usr/bin/env for python.

On the other hand rename all the calls to python from python to python3 making it explicit
and being compliant with PEP 394 -- The "python" Command on Unix-Like Systems:
https://www.python.org/dev/peps/pep-0394/

Remove the sheebang from src/graphics/GraphicsConverter.cpp because it is not necessary.

Some small whitespace changes.

development/cmake/doc/ReplaceValues.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 
 from __future__ import print_function
 

development/cmake/po/cat.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 
 from __future__ import print_function
 

development/cmake/po/unix2dos.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 
 ###############
 import sys

development/cmake/po/update-gmo.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 
 ###############
 import sys, os, shutil

development/tools/gen_lfuns.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file gen_lfuns.py

development/tools/generate_symbols_images.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file generate_symbols_images.py

development/tools/generate_symbols_list.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file generate_symbols_images.py

development/tools/mergepo.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file mergepo.py

development/tools/unicodesymbols.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file unciodesymbols.py

development/tools/updatedocs.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file updatedocs.py

development/tools/updatelayouts.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file updatelayouts.py

po/lyx_pot.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file lyx_pot.py
@@ -698,5 +698,3 @@ if __name__ == '__main__':
         encodings_l10n(input_files, output, base)
     else:
         languages_l10n(input_files, output, base)
-
-

po/postats.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 # Copyright (C) 2007 Michael Gerz <michael.gerz@teststep.org>
 # Copyright (C) 2007 José Matos <jamatos@lyx.org>

src/graphics/GraphicsConverter.cpp

@@ -287,8 +287,7 @@ static void build_script(string const & doc_fname,
 	LYXERR(Debug::GRAPHICS, "build_script ... ");
 	typedef Graph::EdgePath EdgePath;
 
-	script << "#!/usr/bin/env python\n"
-		  "# -*- coding: utf-8 -*-\n"
+	script << "# -*- coding: utf-8 -*-\n"
 		  "import os, shutil, sys\n\n"
 		  "def unlinkNoThrow(file):\n"
 		  "  ''' remove a file, do not throw if an error occurs '''\n"

src/tex2lyx/test/runtests.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # file src/tex2lyx/test/runtests.py
@@ -161,4 +161,3 @@ def getlyxinput(lyx, lyxfx, lyxf, uselyx2lyx):
 
 if __name__ == "__main__":
     main(sys.argv)
-