Another suggestion after first contact, change

<http://get.pulumi.com|get.pulumi.com>

to curl silently. 😛

...
Step 4/5 : RUN curl -fsSL <https://get.pulumi.com> | bash -s -- --version $PULUMI_VERSION     && mv ~/.pulumi/bin/* /usr/local/bin     && pulumi version
 ---> Running in 8435a5532c49
=== Installing Pulumi v1.0.0 ===
+ Downloading <https://get.pulumi.com/releases/sdk/pulumi-v1.0.0-linux-x64.tar.gz>...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 46.3M  100 46.3M    0     0  29.2M      0  0:00:01  0:00:01 --:--:-- 29.2M
+ Extracting to /root/.pulumi/bin
...