Merge pull request #8314 from kasper3/patch-1

Check if tput command exists before using it

scripts/docker/alpine.3.6/Dockerfile

@@ -6,8 +6,6 @@
 # Dockerfile that creates a container suitable to build dotnet-cli
 FROM microsoft/dotnet-buildtools-prereqs:alpine-3.6-3148f11-20171119021156
 
-RUN apk add --no-cache sudo ncurses
-
 # This Dockerfile doesn't use the USER_ID, but the parameter needs to be declared to prevent docker
 # from issuing a warning
 ARG USER_ID=0

scripts/obtain/dotnet-install.sh

@@ -22,7 +22,7 @@ exec 3>&1
 
 # Setup some colors to use. These need to work in fairly limited shells, like the Ubuntu Docker container where there are only 8 colors.
 # See if stdout is a terminal
-if [ -t 1 ]; then
+if [ -t 1 ] && command -v tput > /dev/null; then
     # see if it supports colors
     ncolors=$(tput colors)
     if [ -n "$ncolors" ] && [ $ncolors -ge 8 ]; then