Allow setting DIB_PIP_RETRIES

Pip now supports retries on failure. If setting multiple pypi mirrors a
fallback will not occure until the failures have finished for the first
mirror. This can cause a substantial delay if mirror fallback occurs a
lot.

Change-Id: Iad37a9015a2d5c861a345a111bd1725b965a42d3

elements/pypi/README.rst

@@ -24,10 +24,16 @@ the first mirror to be used, the last listed mirror is used as the pydistutils
 index. NB: The sort order for these variables is a simple string sort - if you
 have more than 9 additional mirrors, some care will be needed.
 
+You can also set the number of retries that occur on failure by setting the
+DIB\_PIP\_RETRIES environment variable. If setting fallback pip mirrors you
+typically want to set this to 0 to prevent the need to fail multiple times
+before falling back.
+
 A typical use of this element is thus:
 export DIB\_PYPI\_MIRROR\_URL=http://site/pypi/Ubuntu-13.10
 export DIB\_PYPI\_MIRROR\_URL\_1=http://site/pypi/
 export DIB\_PYPI\_MIRROR\_URL\_2=file:///tmp/pypi
+export DIB\_PIP\_RETRIES=0
 
 [devpi-server](https://git.openstack.org/cgit/openstack-infra/pypi-mirro://pypi.python.org/pypi/devpi-server)
 can be useful in making a partial PyPI mirror suitable for building images. For

elements/pypi/pre-install.d/00-configure-pypi-mirror

@@ -44,10 +44,13 @@ def main():
         use_pypi_python_org = False
     if use_pypi_python_org:
         indices.append('https://pypi.python.org/simple')
+    retries = os.environ.get('DIB_PIP_RETRIES')
     with file(home + '/.pip/pip.conf', 'wt') as output:
         output.write('[global]\n')
         output.write('log = %s/pip.log\n' % (home,))
         output.write('index-url = %s\n' % (indices[0],))
+        if retries is not None:
+            output.write('retries = %s\n' % retries)
         for index in indices[1:]:
             output.write('extra-index-url = %s\n' % (index,))
     with file(home + '/.pydistutils.cfg', 'wt') as output: