Test: Symbolic Arithmetic

[ianfhunter]

Is your feature request related to a problem? Please describe.
Legacy Test that needs to be added to our test suit

Describe the solution you'd like
a roll of dF! should fail with an error as symbolic dice are not supported for explosions
Add to pytest tests in tests/python

Describe alternatives you've considered

Additional context

• Subtraction can make no sense for string dice if they do not contain the same items
• You also should not be able to add numbers and strings together
• And you cannot use strings as a condition on numbers
  • You can do the reverse though.
• String Math does not make sense most of the time

Legacy Tests (may be incorrect/outdated)

roll	low	high	passes
"df+df"	--	++	False
"10df-2df"	-	++++++++,	True
"2df-20df"	++++++++++++++++++	------------------	True
"d10+df"	-----------	+++++++++++	True
"2d4x3df"	----	++++++++++++++++++++++++++++	True
"2dF x 2d4"	"--:--"	"++:++:++:++:++:++:++:++"	False
"3df!"	---	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++	False

Error Cases:
"dF*dF"
"dF/dF"
"dF|dF"
"dF%dF"
"dF+dF","--","++",False
"dF-dF"

"dF*d3", "-","+++", False
"dF/d3"
"dF|d3"
"dF%d3"
"dF+d3"
"dF-d3"