Problems with "Introduction to tf2" Tutorial

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I'm trying to run through the Introduction to tf2 tutorial provided here. I've installed all of the dependencies successfully, or at least without error; however, when I run the launch command I see this:

roslaunch -v turtle_tf2 turtle_tf2_demo.launch 
... logging to /home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/roslaunch-20079-4907.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

... loading XML file [/opt/ros/noetic/etc/ros/roscore.xml]
... executing command param [rosversion roslaunch]
Added parameter [/rosversion]
... executing command param [rosversion -d]
Added parameter [/rosdistro]
Added core node of type [rosout/rosout] in namespace [/]
... loading XML file [/opt/ros/noetic/share/turtle_tf2/launch/turtle_tf2_demo.launch]
Added node of type [turtlesim/turtlesim_node] in namespace [/]
Added node of type [turtlesim/turtle_teleop_key] in namespace [/]
Added parameter [/scale_linear]
Added parameter [/scale_angular]
Added parameter [/turtle1_tf2_broadcaster/turtle]
Added node of type [turtle_tf2/turtle_tf2_broadcaster.py] in namespace [/]
Added parameter [/turtle2_tf2_broadcaster/turtle]
Added node of type [turtle_tf2/turtle_tf2_broadcaster.py] in namespace [/]
Added node of type [turtle_tf2/turtle_tf2_listener.py] in namespace [/]
started roslaunch server http://localhost:39285/

SUMMARY
========

PARAMETERS
 * /rosdistro: noetic
 * /rosversion: 1.15.14
 * /scale_angular: 2.0
 * /scale_linear: 2.0
 * /turtle1_tf2_broadcaster/turtle: turtle1
 * /turtle2_tf2_broadcaster/turtle: turtle2

NODES
  /
    sim (turtlesim/turtlesim_node)
    teleop (turtlesim/turtle_teleop_key)
    turtle1_tf2_broadcaster (turtle_tf2/turtle_tf2_broadcaster.py)
    turtle2_tf2_broadcaster (turtle_tf2/turtle_tf2_broadcaster.py)
    turtle_pointer (turtle_tf2/turtle_tf2_listener.py)

auto-starting new master
process[master]: started with pid [4918] ROS_MASTER_URI=http://localhost:11311 setting /run_id to ec83aa5a-fc77-11ec-be1e-d963878005dd process[rosout-1]: started with pid [4931]
started core service [/rosout]
process[sim-2]: started with pid [4938] process[teleop-3]: started with pid [4939] process[turtle1_tf2_broadcaster-4]: started with pid [4940]
/usr/bin/env: ‘python’: Permission denied
process[turtle2_tf2_broadcaster-5]: started with pid [4942]
/usr/bin/env: ‘python’: Permission denied
[turtle1_tf2_broadcaster-4] process has died [pid 4940, exit code 126, cmd /opt/ros/noetic/lib/turtle_tf2/turtle_tf2_broadcaster.py __name:=turtle1_tf2_broadcaster __log:=/home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/turtle1_tf2_broadcaster-4.log]. log file: /home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/turtle1_tf2_broadcaster-4*.log [turtle2_tf2_broadcaster-5] process has died [pid 4942, exit code 126, cmd /opt/ros/noetic/lib/turtle_tf2/turtle_tf2_broadcaster.py __name:=turtle2_tf2_broadcaster __log:=/home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/turtle2_tf2_broadcaster-5.log]. log file: /home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/turtle2_tf2_broadcaster-5*.log process[turtle_pointer-6]: started with pid [4947]
/usr/bin/env: ‘python’: Permission denied
Reading from keyboard
---------------------------
Use arrow keys to move the turtle. 'q' to quit.
[turtle_pointer-6] process has died [pid 4947, exit code 126, cmd /opt/ros/noetic/lib/turtle_tf2/turtle_tf2_listener.py __name:=turtle_pointer __log:=/home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/turtle_pointer-6.log]. log file: /home/chainley/.ros/log/ec83aa5a-fc77-11ec-be1e-d963878005dd/turtle_pointer-6*.log 

At first I thought it might be an error of permissions, so I navigated to the offending scripts and entered:

$: sudo chmod u+x turtle_tf2_broadcaster.py
$: sudo chmod u+x turtle_tf2_listener.py

That didn't fix it, so I also tried:

$: sudo rosdep fix-permissions

That didn't work either. On further investigation, my system doesn't have the folder listed in the error; /usr/bin/env doesn't actually exist. Not sure what to do about that.

Any suggestions?