erp5: Add google-api-python-client that is requred for Google OAuth

pin uritemplate to 0.6 because google-api-python-client does not work with with version 3.0 of uritemplate

/cc @kazuhiko @jerome 

/reviewed-on nexedi/slapos!134

stack/erp5/buildout.cfg

 [buildout]
+
 extends =
 # Exact version of Zope
   ztk-versions.cfg
@@ -571,6 +572,8 @@ eggs = ${neoppod:eggs}
 
 # Needed for parsing .po files from our Localizer subset
   polib
+# Needed for Google OAuth
+  google-api-python-client
 
 # Used by ERP5 Jupyter backend
   ipykernel
@@ -638,6 +641,9 @@ python-magic = 0.4.12+SlapOSPatched001
 # specify dev version to be sure that an old released version is not used
 cloudooo = 1.2.5-dev
 
+uritemplate = 3.0.0
+google-api-python-client = 1.6.1
+
 # use newer version than specified in ZTK
 PasteDeploy = 1.5.2
 Pygments = 2.1.3