Those "ERROR:root:" can be red herring. I think those are benign & should be changed to warning

enne: can you please try setting:
export GYP_DEFINES=fetch_telemetry_dependencies=1

and running "gclient sync" in your workspace?

At that point I think all of these Telemetry-related errors should go away when trying to run these presubmit scripts.

Hmm! I get the same warning during gclient sync with that define (and then the same thing as above when uploading after that).

--snip--
Running hooks:  72% (39/54) fetch_telemetry_binary_dependencies   
________ running 'vpython src/tools/perf/conditionally_execute --gyp-condition fetch_telemetry_dependencies=1 src/third_party/catapult/telemetry/bin/fetch_telemetry_binary_dependencies' in '/work'
WARNING:root:Unable to import cv2 due to: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by /work/src/third_party/catapult/telemetry/third_party/cv2/lib/cv2_linux_x86_64_85be3046d2fef651206d7daadbd1b34af2a005f5/cv2.so)
--snip--


It does seem like my libstdc++ doesn't have the right version, though.

enne@tropy:~$ strings /usr/lib/x86_64-linux-gnu/libstdc++.so.6 | grep GLIBCXX
GLIBCXX_3.4
GLIBCXX_3.4.1
GLIBCXX_3.4.2
GLIBCXX_3.4.3
GLIBCXX_3.4.4
GLIBCXX_3.4.5
GLIBCXX_3.4.6
GLIBCXX_3.4.7
GLIBCXX_3.4.8
GLIBCXX_3.4.9
GLIBCXX_3.4.10
GLIBCXX_3.4.11
GLIBCXX_3.4.12
GLIBCXX_3.4.13
GLIBCXX_3.4.14
GLIBCXX_3.4.15
GLIBCXX_3.4.16
GLIBCXX_3.4.17
GLIBCXX_3.4.18
GLIBCXX_3.4.19
GLIBCXX_DEBUG_MESSAGE_LENGTH

There's no 3.4.20 there.  I'm still running Trusty though, so maybe I'm just out of date?

The warning about being able to load cv2 started in the past couple of months and we're going to ditch the dependency soon by switching these tests to run with Infra's new vpython. But that's not why the presubmit check is failing. It shouldn't cause things to have a nonzero exit code.

Can you manually run ./content/test/gpu/run_unittests.py in your src/ directory? What does it report?

The error looks identical to what git cl upload gives me:

enne@tropy:/work/src$ ./content/test/gpu/run_unittests.py 
WARNING:root:Unable to import cv2 due to: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by /work/src/third_party/catapult/telemetry/third_party/cv2/lib/cv2_linux_x86_64_85be3046d2fef651206d7daadbd1b34af2a005f5/cv2.so)
ERROR:root:Dependency flash could not be found or fetched from cloud storage for platform linux_x86_64. Error: None
ERROR:root:Error when trying to prefetch paths for linux_x86_64: No file could be found locally, and no file to download from cloud storage for flash on platform linux_x86_64
**Non zero exit code**
If you don't see any error stack, this could have been a native crash. Consider installing faulthandler (https://faulthandler.readthedocs.io/) for more useful error message

Debugging with enne in real time, this is another incidence of  Issue 716241 . However, it looks like we may now have a possible fix for that, in the form of vpython!