update deps

dev_requirements.txt

-pyldap>=3.0.0  # here instead of requirements.txt so rtfd can build
-Sphinx>=1.5.5
+python-ldap==3.2.0  # here instead of requirements.txt so rtfd can build
+Sphinx==2.1.2
 
 -r requirements.txt

requirements.txt

-Flask>=0.12.4
-mock>=2.0.0  # for ci
+Flask==1.1.1
+mock==3.0.5  # for ci