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Error: While constructing the build plan, the following exceptions were encountered:

In the dependencies for debug-me-1.20170810:
    posix-pty must match (>=0.2.1), but the stack configuration has no specified version (latest applicable is
needed since debug-me-1.20170810 is a build target.

Recommended action: try adding the following to your extra-deps in /builddir/debug-me-1.20170810/stack.yaml:
- posix-pty-

You may also want to try the 'stack solver' command
Plan construction failed.

I couldn't see posix-pty in the lts package list? Was it erroneously removed from stack.yaml?