Update babel from 2.5.3 to 2.6.0

requirements/docs.txt

@@ -17,9 +17,9 @@ alabaster==0.7.10 \
     --hash=sha256:2eef172f44e8d301d25aff8068fddd65f767a3f04b5f15b0f4922f113aa1c732 \
     --hash=sha256:37cdcb9e9954ed60912ebc1ca12a9d12178c26637abdf124e3cde2341c257fe0
 # babel is required by Sphinx, django-babel, puente
-Babel==2.5.3 \
-    --hash=sha256:ad209a68d7162c4cff4b29cdebe3dec4cef75492df501b0049a9433c96ce6f80 \
-    --hash=sha256:8ce4cb6fdd4393edd323227cba3a077bceb2a6ce5201c902c65e730046f41f14
+Babel==2.6.0 \
+    --hash=sha256:6778d85147d5d85345c14a26aada5e478ab04e39b078b0745ee6870c2b5cf669 \
+    --hash=sha256:8cba50f48c529ca3fa18cf81fa9403be176d374ac4d60738b839122dfaaa3d23
 # docutils is required by Sphinx
 docutils==0.14 \
     --hash=sha256:7a4bd47eaf6596e1295ecb11361139febe29b084a87bf005bf899f9a42edc3c6 \