Gns 80 cloud image

For review.
Keiron, read up on string formatting at https://docs.python.org/3.3/library/string.html#string.Formatter

Section 6.1.3.2 gives examples of the #{substitution} syntax that would be good to use.

Probably a better choice would be to use the string.Template formatter in section 6.1.4 on the same page.  You can put the script in a separate file, read it in in this function and apply the variable substitutions.

For future reference, lines with
```
script += "stuff"
```
are ported Java code and should be replaced with
```
script = textwrap.dedent("""\
    #!/bin/bash
    echo "hello"
""")
```