dev-python/certifi: Bump to v2018.04.16

Ebuild changes:
===============
- We no longer install bundled cacert.pem. Instead we
  refer to system's CA store.

Closes: https://github.com/gentoo/gentoo/pull/8109
Closes: https://bugs.gentoo.org/627558
Package-Manager: Portage-2.3.31, Repoman-2.3.9

dev-python/certifi/files/certifi-2018.4.16-use-system-cacerts.patch

@@ -0,0 +1,15 @@
+Use system's CA certificate store
+
+--- a/certifi/core.py
++++ b/certifi/core.py
+@@ -19,9 +19,7 @@ class DeprecatedBundleWarning(DeprecationWarning):
+ 
+ 
+ def where():
+-    f = os.path.dirname(__file__)
+-
+-    return os.path.join(f, 'cacert.pem')
++    return "@GENTOO_PORTAGE_EPREFIX@/etc/ssl/certs/ca-certificates.crt"
+ 
+ 
+ def old_where():