package/python-psycopg2: needs python3

python 2 support has been dropped since version 2.9 and
https://github.com/psycopg/psycopg2/commit/d956eaa3b1842a14895685be0d6d5e380fd029fc
resulting in the following build failure since bump to version 2.9.1 in
commit 09417e47d706e5d7d58c0f886b4679064c5175fa:

  File "setup.py", line 117
    f"Unable to find 'pg_config' file in '{self.pg_config_exe}'")
                                                               ^

Fixes:
 - http://autobuild.buildroot.org/results/f8a2cf9eea500e2c617381840b849225f12b56f1

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/python-psycopg2/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_PYTHON_PSYCOPG2
 	bool "python-psycopg2"
+	depends on BR2_PACKAGE_PYTHON3
 	depends on BR2_USE_WCHAR # postgresql
 	select BR2_PACKAGE_POSTGRESQL
 	help
@@ -21,5 +22,7 @@ config BR2_PACKAGE_PYTHON_PSYCOPG2
 	  Psycopg 2 is both Unicode and Python 3 friendly.
 
 	  http://initd.org/psycopg/
+
 comment "python-psycopg2 needs a toolchain w/ wchar"
+	depends on BR2_PACKAGE_PYTHON3
 	depends on !BR2_USE_WCHAR