UPDATE: Desde a atualização do Windows 10 Fall Creators (FCU), o recurso bash foi retirado da versão beta. Agora você pode usar bash e Ubuntu no Windows 10 novamente, se desejar.
No Microsofts Repo BashOnWindows você encontrará o seguinte problema: aplicativo que você está tentando executar não é suportado nesta versão do Windows # 1448
Nele esta explicação é fornecida
The beta was accidentally included in the LTSB release. It was
subsequently disabled because it cannot be updated or even bugfixed
without updating the kernel-mode drivers lxcore.sys and lxss.sys, both
of which are strictly bound to specific versions of the Windows kernel
(for example, work on networking to support some WSL features was
transported into the kernel-mode "Winsock Kernel" core module of the
NT kernel, where it will also be used to provide more socket
functionality to the Win32 usermode Winsock API as well).
The drivers lxcore.sys and lxss.sys (being beta components) are being
maintained directly along the "Fast ring" of the Insider branch of
Windows 10. The "slow ring" provides snapshots of the "fast ring", and
the Current Branch will be replaced roughly this April by another fork
of the Insider branch. Until the Windows Subsystem for Linux loses its
"beta" tag, it will only be available (updates, bugfixes, etc) in the
Current Branch as a snapshot of its state at the date of the fork,
without even bugfixes being backported to the current branch from the
Insider Branch.
Given that even the Current Branch is not currently receiving
bugfixes, upgrades, or likely even security fixes, it would be
impossible to handle bugfixes in LTSB (releases scheduled 2-3 years
apart!) of a feature that is highly incomplete and has already hit
several bugchecks (many bugchecks are also potential security
vulnerabilities, and it is dangerous to use buggy drivers in
kernel-mode).
So a decision was taken by Microsoft to remove this feature from LTSB
until it is out of beta, at which point it will at least have bugs and
security vulnerabilities fixed and backported. On the other hand, this
also means that LTSB will not be receiving this functionality in
stable form until at least 2018 if not 2019.
If you want to use WSL, it is highly recommended to run Insider builds
or at the very least the Current Branch, which receives updates
roughly every nine months.
Longa história curta ... a menos que você esteja fazendo o Windows Insider para as janelas de teste beta 10, você não terá acesso a esse recurso do Windows até que a versão beta termine em 2018 ou 2019.
Uma alternativa para ingressar no programa Windows Insider seria configurar uma máquina virtual executando o Ubuntu