Update examples/bin/dsql scripts to accept Python 3 (#16677)

* Update examples/bin/dsql scripts to accept Python 3

Remove redundant urllib import

Translating to Python3: Changing xrange to range

Translating to Python3: Changing long to int

Translating to Python3: Change urllib2 methods, and fix encoding/decoding issues

Remove unnecessary import

Add option for Python2

Rename files

* Update examples/bin/dsql

Co-authored-by: Benedict Jin <asdf2014@apache.org>

* Resolve PR comments

Add comment in files indicating updates need to be made in both places

Update examples/bin/dsql

Co-authored-by: Benedict Jin <asdf2014@apache.org>

* Update error output when using Python 2.

Co-authored-by: Abhishek Radhakrishnan <abhishek.rb19@gmail.com>

---------

Co-authored-by: Benedict Jin <asdf2014@apache.org>
Co-authored-by: Abhishek Radhakrishnan <abhishek.rb19@gmail.com>

examples/bin/dsql

@@ -21,9 +21,16 @@ PWD="$(pwd)"
 WHEREAMI="$(dirname "$0")"
 WHEREAMI="$(cd "$WHEREAMI" && pwd)"
 
-if [ -x "$(command -v python2)" ]
+if [ -x "$(command -v python3)" ]
 then
-  exec python2 "$WHEREAMI/dsql-main" "$@"
+  exec python3 "$WHEREAMI/dsql-main-py3" "$@"
+elif [ -x "$(command -v python2)" ]
+then
+  echo "Warning: Support for Python 2 will be removed in the future. Please consider upgrading to Python 3"
+  exec python2 "$WHEREAMI/dsql-main-py2" "$@"
+elif [ -x "$(command -v python)" ]
+then
+  exec python "$WHEREAMI/dsql-main-py3" "$@"
 else
-  exec "$WHEREAMI/dsql-main" "$@"
+  echo "python interepreter not found"
 fi

examples/bin/dsql-main → examples/bin/dsql-main-py2

@@ -17,6 +17,11 @@
 # specific language governing permissions and limitations
 # under the License.
 
+# NOTE:
+# Any feature updates to this script must also be reflected in
+# `dsql-main-py3` so that intended changes work for users using
+# Python 2 or 3.
+
 from __future__ import print_function
 
 import argparse