Remove explicit dependency on tabulate; Add comments (sonic-net#336)

Author: jleveque

setup.py

@@ -85,11 +85,19 @@ def get_test_suite():
             'undebug = undebug.main:cli',
         ]
     },
+    # NOTE: sonic-utilities also depends on other packages that are either only
+    # available as .whl files or the latest available Debian packages are
+    # out-of-date and we must install newer versions via pip. These
+    # dependencies cannot be listed here, as this package is built as a .deb,
+    # therefore all dependencies will be assumed to also be available as .debs.
+    # These unlistable dependencies are as follows:
+    # - sonic-config-engine
+    # - swsssdk
+    # - tabulate
     install_requires=[
         'click-default-group',
         'click',
-        'natsort',
-        'tabulate'
+        'natsort'
     ],
     classifiers=[
         'Development Status :: 3 - Alpha',