"SyntaxError: invalid syntax" when running any command with "gclient"

I was attempting to test out the WepGPU implementation [Dawn](), but I've run into an issue. When I run `gclient sync`, python fails with a syntax error.
```
gclient sync
Traceback (most recent call last):
File "/usr/local/bin/gclient", line 6, in
from depot_tools import gclient
File "/usr/local/lib/python3.6/dist-packages/depot_tools/gclient.py", line 199
print 'Overwriting Var("webkit_trunk") with %s' % new_url
^
SyntaxError: invalid syntax
```
I installed `gclient` with the following command:
```
sudo pip3 install gclient
The directory '/home/user/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/user/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting gclient
Downloading https://files.pythonhosted.org/packages/a6/63/c87ffca3801f7f48011c38ae9fc3bffca43d0a8ec58f4fe4e05458d2c35f/gclient-0.7.2.tar.gz (328kB)
100% |████████████████████████████████| 337kB 495kB/s
Installing collected packages: gclient
Running setup.py install for gclient ... done
Successfully installed gclient-0.7.2
```
I'm running Linux Mint 19.1. Running `pip3 --version` gives me `pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)`.

Reproduce the failure with `gclient sync`, then inspect `/usr/local/lib/python3.6/dist-packages/depot_tools/gclient.py` around line 199 and the installed `gclient` entry point. Determine the supported Python runtime and verify that running a gclient command no longer produces the reported SyntaxError.

Written by the indexing model from the issue text.