recipetool/create_buildsys_python: prefix created recipes with python3-

By convention, all python recipes start with "python3-" so update
create_buildsys_python to do this

This rule doesn't apply for packages already starting with "python"

Update recipetool's selftest accordingly

(From OE-Core rev: b0d87440e610b80f763d09784d4a90a148bb3e7b)

Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/recipetool/create_buildsys_python.py

@@ -297,6 +297,11 @@ class PythonRecipeHandler(RecipeHandler):
                 value = ' '.join(str(v) for v in values if v)
 
             bbvar = self.bbvar_map[field]
+            if bbvar == "PN":
+                # by convention python recipes start with "python3-"
+                if not value.startswith('python'):
+                    value = 'python3-' + value
+
             if bbvar not in extravalues and value:
                 extravalues[bbvar] = value