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Here are the two examples I found confusing when playing with f-strings. The first one involves with a NameError:
$ cat test2
f'''
{
FOO
}
'''
$ python3.7m test2
Traceback (most recent call last):
 File "test2", line 5, in <module>
 '''
NameError: name 'FOO' is not defined
It would be better if the error reporter points to the actual line of the error:
$ python3.7m test2
Traceback (most recent call last):
 File "test2", line 3, in <module>
 FOO
NameError: name 'FOO' is not defined
The second one involves a SyntaxError:
$ cat test2 
f'''
{
a b c
}
'''
$ python3.7m test2
 File "<fstring>", line 2
 a b c
 ^
SyntaxError: invalid syntax
It would be better if the line number is relative to the file instead of the expression in f-strings:
$ python3.7m test2
 File "test2", line 3
 a b c
 ^
SyntaxError: invalid syntax
By the way, external checkers like pyflakes also suffers. They rely on ASTs. Nodes in f-strings have their lineno relative to the {...} expression instead of the whole code string. For example:
import ast
code = '''
f'{LOL}'
'''
for node in ast.walk(ast.parse(code, "<stdin>", "exec")):
 if isinstance(node, ast.Name):
 print(node.lineno)
Prints 1 instead of 2.
Another by the way, ruby reports correct line numbers:
$ cat test3 
"
#{
FOO
}
"
$ ruby test3 
test3:3:in `<main>': uninitialized constant FOO (NameError)
$ cat test3 
"
#{
@@
}
"
$ ruby test3
test3:3: `@@' without identifiers is not allowed as a class variable name
test3:3: syntax error, unexpected end-of-input
Added the author and the primary reviewer of issue24965.