schemes: fix a broken check for drive letter conflicts
Flagged by pytype locally. It appears to have regressed in 1863584f2fba (not
yet released).
This seems like an obvious typo- `dict.isalpha()` is nonsense. There's no crash
though because `schemes` is pre-populated with 5 schemes (that are all now
defunct), so the length of the dict is never 1, so it's impossible to abort.
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2