add oauth support

CHANGELOG.md

@@ -1,6 +1,8 @@
 Unreleased
 ----------
- -
+ - `Session` now supports authorization using OAuth2 tokens.  Use the `token=` parameter in the constructor when 
+ an existing access token token is known.  Alternatively, ommitting the `username=` and `password=` parameters
+ will now prompt the user for an auth code.
 
 v1.5.9 (2021-06-09)
 -------------------

doc/index.rst

@@ -270,6 +270,9 @@ can be instantiated using simply the hostname:
 
     >>> s = Session(hostname)
 
+If a username and password are not provided, and the SAS Viya server has **not** been configured for Kerberos then
+**sasctl** will attempt to connect using OAuth2 authorization codes.  In this situation, you may be prompted to open
+a URL in your browser, retrieve an authorization code, and then enter it before sasctl can connect.
 
 The final method for supplying credentials is also simple and straight-forward: environment variables.
 
@@ -278,7 +281,8 @@ The final method for supplying credentials is also simple and straight-forward:
  - :envvar:`SASCTL_SERVER_NAME`
  - :envvar:`SASCTL_USER_NAME`
  - :envvar:`SASCTL_PASSWORD`
-
+ - :envvar:`SASCTL_CLIENT_ID`
+ - :envvar:`SASCTL_CLIENT_SECRET`
 
 
 
@@ -374,6 +378,16 @@ The name of the user that will be used when creating the :class:`.Session` insta
 
 Password for authentication to the SAS Viya server.
 
+.. envvar:: SASCTL_CLIENT_ID
+
+OAuth2 client ID used during authorization.
+
+.. envvar:: SASCTL_CLIENT_SECRET
+
+OAuth2 client secret used during authorization.
+
+
+
 
 Contributor Guide
 -----------------

setup.py

@@ -47,6 +47,8 @@ def get_file(filename):
         'scikit-learn',
         'requests',
         'six >= 1.11',
+        'pyyaml',
+        'packaging',
         'futures ; python_version <= "2.7"'
     ],
     extras_require={