Add extra version of py-zipp (#15118)

* Add extra version of py-zipp

* Update package.py

var/spack/repos/builtin/packages/py-zipp/package.py

@@ -13,8 +13,9 @@ class PyZipp(PythonPackage):
     url      = "https://pypi.io/packages/source/z/zipp/zipp-0.6.0.tar.gz"
 
     version('0.6.0', sha256='3718b1cbcd963c7d4c5511a8240812904164b7f381b647143a89d3b98f9bcd8e')
+    version('0.5.1', sha256='ca943a7e809cc12257001ccfb99e3563da9af99d52f261725e96dfe0f9275bc3')
 
     depends_on('python@2.7:', type=('build', 'run'))
     depends_on('py-setuptools', type='build')
     depends_on('py-setuptools-scm@1.15.0:', type='build')
-    depends_on('py-more-itertools', type=('build', 'run'))
+    depends_on('py-more-itertools', type=('build', 'run'), when='@0.6.0:')