In _raw(), all objects (except for lists, EOF, and TIMEOUT) go through this process:

• The object is converted to a string
• Then the object is converted to its escaped representation (using repr)
• This new escaped representation adds quotes around the object, which we remove using [1:-1]
• Finally, we wrap the entire thing in double quotes.

There's a few concerns I have with this:

• Why double quotes? Why not single quotes in cases where single quotes weren't in the string? And why remove quotes just to add them back in?
• Since Mismatch and Missing call the _raw function, even if you enter a non-string input, the error message will spit out what looks to be a string. Take a look at this code:

from check50 import Mismatch

raise Mismatch(1, "1")

which outputs

expected: "1"
actual:   "1"

Or this code:

from check50 import Missing

raise Missing("1", [1,2,3])

which outputs

Did not find "1" in ""1"\n"2"\n"3""