upload-pypi: make repository url optional

The current default URL returns an error.  The error message suggests
that we just omit the URL entirely from the config and let twine
handle it.  That's what this patch does.

Change-Id: I83b2eb30e3c93690dbe03052cd3f20a73c110350

roles/upload-pypi/README.rst

@@ -19,12 +19,12 @@ Upload python packages to PyPI
   .. zuul:rolevar:: repository
      :default: pypi
 
-     Name of the repository to upload to
+     Name of the repository to upload to.
 
   .. zuul:rolevar:: repository_url
-     :default: https://pypi.python.org/pypi
+     :default: The built-in twine default for the production pypi.org service.
 
-     URL of the PyPI repostory
+     URL of the PyPI repostory.
 
 .. zuul:rolevar:: pypi_path
    :default: src/{{ zuul.project.canonical_name }}/dist

roles/upload-pypi/defaults/main.yaml

@@ -1,5 +1,5 @@
 ---
 pypi_path: "src/{{ zuul.project.canonical_name }}/dist"
 pypi_repository: "{{ pypi_info.repository|default('pypi') }}"
-pypi_repository_url: "{{ pypi_info.repository_url|default('https://pypi.python.org/pypi') }}"
+pypi_repository_url: "{{ pypi_info.repository_url|default(None) }}"
 pypi_twine_executable: twine

roles/upload-pypi/templates/.pypirc.j2

@@ -3,6 +3,8 @@ index-servers=
   {{ pypi_repository }}
 
 [{{ pypi_repository }}]
+{% if pypi_repository_url %}
 repository:{{ pypi_repository_url }}
+{% endif %}
 username:{{ pypi_info.username }}
 password:{{ pypi_info.password }}