azure-pipelines-tasks: Powershell task goes into 'debug' mode for some errors which hangs the pipeline forever

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Question, Bug, or Feature?
Bug.

Enter Task Name: PowerShell@2

Environment

• Server - Azure Pipelines

  • If using Azure Pipelines, provide the account name, team project name, build definition name/build number: dev.azure.com/vcpkg, “public”, “microsoft.vcpkg.pr”.

• Agent - Hosted or Private: Private, Windows Server 2019, 1.628.2

Issue Description

This report is in response to the failed build here: https://dev.azure.com/vcpkg/public/_build/results?buildId=37246&view=logs&j=84da4f4a-968a-5b5c-16e9-f444c845396d&t=8cdf6620-a129-5b70-3f3e-822630a64446

You can see our tool, vcpkg, invoked pacman to download some msys2 things, which failed. That all is fine and is our fault for depending on flaky external servers, not the agent. However, after that fails it looks like the task crashes starting from the " Working Directory: C:/agent/_work/1/s/downloads/tools/msys2" line:

Building package ffmpeg[avresample,core]:arm64-windows...
Could not locate cached archive: C:\agent\_work\1\s\archives\dd\dd46a9137e8d69b1bd7857a16f54b496bdf40dfa.zip
-- Downloading https://github.com/ffmpeg/ffmpeg/archive/n4.2.tar.gz...
-- Extracting source C:/agent/_work/1/s/downloads/ffmpeg-ffmpeg-n4.2.tar.gz
-- Applying patch 0001-create-lib-libraries.patch
-- Applying patch 0003-fix-windowsinclude.patch
-- Applying patch 0004-fix-debug-build.patch
-- Applying patch 0005-fix-libvpx-linking.patch
-- Applying patch 0006-fix-StaticFeatures.patch
-- Using source at C:/agent/_work/1/s/buildtrees/ffmpeg/src/n4.2-a4d149a5c6
-- Downloading https://www.tortall.net/projects/yasm/snapshots/v1.3.0.6.g1962/yasm-1.3.0.6.g1962.exe...
-- Installing: C:/agent/_work/1/s/downloads/tools/yasm/1.3.0.6/yasm.exe
-- Acquiring MSYS2...
-- Downloading https://sourceforge.net/projects/msys2/files/Base/x86_64/msys2-base-x86_64-20190524.tar.xz/download...
gpg: /etc/pacman.d/gnupg/trustdb.gpg: trustdb created
gpg: no ultimately trusted keys found
gpg: starting migration from earlier GnuPG versions
gpg: porting secret keys from '/etc/pacman.d/gnupg/secring.gpg' to gpg-agent
gpg: migration succeeded
gpg: Generating pacman keyring master key...
gpg: key 8A01FBB0ECFCE852 marked as ultimately trusted
gpg: directory '/etc/pacman.d/gnupg/openpgp-revocs.d' created
gpg: revocation certificate stored as '/etc/pacman.d/gnupg/openpgp-revocs.d/F341A5A61B865E09770CB3418A01FBB0ECFCE852.rev'
gpg: Done
==> Updating trust database...
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
==> Appending keys from msys2.gpg...
==> Locally signing trusted keys in keyring...
  -> Locally signing key D55E7A6D7CE9BA1587C0ACACF40D263ECA25678A...
  -> Locally signing key 123D4D51A1793859C2BE916BBBE514E53E0D0813...
  -> Locally signing key B91BCF3303284BF90CC043CA9F418C233E652008...
  -> Locally signing key 9DD0D4217D75A33B896159E6DA7EF2ABAEEA755C...
==> Importing owner trust values...
gpg: setting ownertrust to 4
gpg: setting ownertrust to 4
gpg: setting ownertrust to 4
gpg: inserting ownertrust of 4
==> Updating trust database...
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   4  trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: depth: 1  valid:   4  signed:   3  trust: 0-, 0q, 0n, 4m, 0f, 0u
gpg: depth: 2  valid:   3  signed:   0  trust: 3-, 0q, 0n, 0m, 0f, 0u
:: Synchronizing package databases...
downloading mingw32.db...
downloading mingw32.db.sig...
downloading mingw64.db...
downloading mingw64.db.sig...
downloading msys.db...
downloading msys.db.sig...
:: Starting core system upgrade...
warning: resolving dependencies...
terminate other MSYS2 programs before proceeding
looking for conflicting packages...

Packages (8) bash-4.4.023-2  filesystem-2020.02-2  libzstd-1.4.4-2  mintty-1~3.1.4-1  msys2-runtime-3.1.4-1  pacman-5.2.1-6  pacman-mirrors-20200329-1  zstd-1.4.4-2

Total Download Size:   16.96 MiB
Total Installed Size:  65.76 MiB
Net Upgrade Size:      -3.96 MiB

:: Proceed with installation? [Y/n] 
:: Retrieving packages...
downloading msys2-runtime-3.1.4-1-x86_64.pkg.tar.zst...
downloading bash-4.4.023-2-x86_64.pkg.tar.xz...
downloading filesystem-2020.02-2-x86_64.pkg.tar.xz...
downloading mintty-1~3.1.4-1-x86_64.pkg.tar.xz...
downloading pacman-mirrors-20200329-1-any.pkg.tar.xz...
downloading libzstd-1.4.4-2-x86_64.pkg.tar.xz...
downloading zstd-1.4.4-2-x86_64.pkg.tar.xz...
downloading pacman-5.2.1-6-x86_64.pkg.tar.xz...
checking keyring...
checking package integrity...
loading package files...
error: could not open file /var/cache/pacman/pkg/msys2-runtime-3.1.4-1-x86_64.pkg.tar.zst: Child process exited with status 127
error: failed to commit transaction (cannot open package file)
Errors occurred, no packages were upgraded.
-- Acquiring MSYS2... OK
-- Acquiring MSYS Packages...
CMake Error at scripts/cmake/vcpkg_execute_required_process.cmake:72 (message):
    Command failed: C:/agent/_work/1/s/downloads/tools/msys2/msys64/usr/bin/bash.exe --noprofile --norc -c "pacman -Sy --noconfirm --needed perl gcc diffutils make"
    Working Directory: C:/agent/_work/1/s/downloads/tools/msys2
    Error code: 1
Entering debug mode. Use h or ? for help. 

At 
C:\agent\_work\_tasks\PowerShell_e213ff0f-5d5c-4791-802d-52ea3e7be1f1\2.169.0\ps_modules\VstsTaskSdk\ToolFunctions.ps1:
113 char:13

+         if ($originalEncoding) {

+             ~~~~~~~~~~~~~~~~~
[DBG]: PS C:\agent\_work\1\s>> 

It looks like this line is being highlighted for some reason: https://github.com/microsoft/azure-pipelines-task-lib/blob/c532de60cd68ba382b17d574c669333beabe0b9f/powershell/VstsTaskSdk/ToolFunctions.ps1#L113

Nothing a build does should be putting the whole agent out of commission.