python-constantly: new package

This is a new requirement for the Twisted package.

From the readme:

A library that provides symbolic constant support. It includes
collections and constants with text, numeric, and bit flag values.
Originally twisted.python.constants from the Twisted project.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

lang/python/python-constantly/Makefile

@@ -0,0 +1,69 @@
+#
+# Copyright (C) 2018 OpenWrt.org
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=python-constantly
+PKG_VERSION:=15.1.0
+PKG_RELEASE:=1
+
+PKG_SOURCE:=constantly-$(PKG_VERSION).tar.gz
+PKG_SOURCE_URL:=https://files.pythonhosted.org/packages/source/c/constantly
+PKG_HASH:=586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35
+
+PKG_BUILD_DIR:=$(BUILD_DIR)/$(BUILD_VARIANT)-constantly-$(PKG_VERSION)
+
+PKG_LICENSE:=MIT
+PKG_LICENSE_FILES:=LICENSE
+PKG_MAINTAINER:=Jeffery To <jeffery.to@gmail.com>
+
+include $(INCLUDE_DIR)/package.mk
+include ../python-package.mk
+include ../python3-package.mk
+
+PKG_UNPACK:=$(HOST_TAR) -C $(PKG_BUILD_DIR) --strip-components=1 -xzf $(DL_DIR)/$(PKG_SOURCE)
+
+define Package/python-constantly/Default
+  SECTION:=lang
+  CATEGORY:=Languages
+  SUBMENU:=Python
+  URL:=https://github.com/twisted/constantly
+endef
+
+define Package/python-constantly
+$(call Package/python-constantly/Default)
+  TITLE:=Symbolic constants in Python
+  DEPENDS:=+PACKAGE_python-constantly:python-light
+  VARIANT:=python
+endef
+
+define Package/python3-constantly
+$(call Package/python-constantly/Default)
+  TITLE:=Symbolic constants in Python
+  DEPENDS:=+PACKAGE_python3-constantly:python3-light
+  VARIANT:=python3
+endef
+
+define Package/python-constantly/description
+A library that provides symbolic constant support. It includes
+collections and constants with text, numeric, and bit flag values.
+Originally twisted.python.constants from the Twisted project.
+endef
+
+define Package/python3-constantly/description
+$(call Package/python-constantly/description)
+.
+(Variant for Python3)
+endef
+
+$(eval $(call PyPackage,python-constantly))
+$(eval $(call BuildPackage,python-constantly))
+$(eval $(call BuildPackage,python-constantly-src))
+
+$(eval $(call Py3Package,python3-constantly))
+$(eval $(call BuildPackage,python3-constantly))
+$(eval $(call BuildPackage,python3-constantly-src))