Define %python2 and %python3

See https://pagure.io/packaging-committee/issue/907

Redefine %__pythonX to change the behavior of %pythonX, %pythonX_version, etc.
Use %pythonX in spec.

macros.python2

@@ -1,4 +1,9 @@
+# use the underscored macros to redefine the behavior of %%python2_version etc.
 %__python2 /usr/bin/python2
+
+# use the non-underscored macros to refer to Python in spec, etc.
+%python2 %__python2
+
 %python2_sitelib %(%{__python2} -Esc "from distutils.sysconfig import get_python_lib; print(get_python_lib())")
 %python2_sitearch %(%{__python2} -Esc "from distutils.sysconfig import get_python_lib; print(get_python_lib(1))")
 %python2_version %(%{__python2} -Esc "import sys; sys.stdout.write('{0.major}.{0.minor}'.format(sys.version_info))")

macros.python3

@@ -1,4 +1,9 @@
+# use the underscored macros to redefine the behavior of %%python3_version etc.
 %__python3 /usr/bin/python3
+
+# use the non-underscored macros to refer to Python in spec, etc.
+%python3 %__python3
+
 %python3_sitelib %(%{__python3} -Ic "from distutils.sysconfig import get_python_lib; print(get_python_lib())")
 %python3_sitearch %(%{__python3} -Ic "from distutils.sysconfig import get_python_lib; print(get_python_lib(1))")
 %python3_version %(%{__python3} -Ic "import sys; sys.stdout.write(sys.version[:3])")

python-rpm-macros.spec

@@ -1,6 +1,6 @@
 Name:           python-rpm-macros
 Version:        3
-Release:        37%{?dist}
+Release:        38%{?dist}
 Summary:        The unversioned Python RPM macros
 
 License:        MIT
@@ -71,6 +71,9 @@ install -m 644 %{SOURCE0} %{SOURCE1} %{SOURCE2} %{SOURCE3} %{SOURCE4} \
 
 
 %changelog
+* Fri Sep 27 2019 Miro Hrončok <mhroncok@redhat.com> - 3-38
+- Define %%python2 and %%python3
+
 * Wed Aug 15 2018 Miro Hrončok <mhroncok@redhat.com> - 3-37
 - Make %%py_byte_compile terminate build on SyntaxErrors (#1616219)