Install pytz by default as a dependency

It's possible for users to switch between experimental Python types and
the old types on the fly and is not something they will decide when
installing the module. So the module must include pytz as a required
dependency.

Author: hashhar

setup.py

@@ -28,7 +28,7 @@
 kerberos_require = ["requests_kerberos"]
 sqlalchemy_require = ["sqlalchemy~=1.3"]
 
-all_require = ["pytz"] + kerberos_require + sqlalchemy_require
+all_require = kerberos_require + sqlalchemy_require
 
 tests_require = all_require + [
     # httpretty >= 1.1 duplicates requests in `httpretty.latest_requests`
@@ -74,7 +74,7 @@
         "Topic :: Database :: Front-Ends",
     ],
     python_requires='>=3.7',
-    install_requires=["requests"],
+    install_requires=["pytz", "requests"],
     extras_require={
         "all": all_require,
         "kerberos": kerberos_require,