Improve phrasing for single term incompatibilities (#9953)

It makes more sense to say "cannot be used" rather than "is
incompatible" when the term is a single package

crates/uv-resolver/src/pubgrub/report.rs

@@ -204,12 +204,8 @@ impl ReportFormatter<PubGrubPackage, Range<Version>, UnavailableReason>
                         _ => (),
                     }
                 }
-                if let [(p, t)] = slice {
+                if slice.len() == 1 {
-                    if PackageTerm::new(p, t, self).plural() {
+                    result.push_str(" cannot be used");
-                        result.push_str(" are incompatible");
-                    } else {
-                        result.push_str(" is incompatible");
-                    }
                 } else {
                     result.push_str(" are incompatible");
                 }
@@ -1444,22 +1440,6 @@ impl PackageTerm<'_> {
             formatter,
         }
     }
-
-    /// Returns `true` if the predicate following this package term should be singular or plural.
-    fn plural(&self) -> bool {
-        match self.term {
-            Term::Positive(set) => self.formatter.compatible_range(self.package, set).plural(),
-            Term::Negative(set) => {
-                if set.as_singleton().is_some() {
-                    false
-                } else {
-                    self.formatter
-                        .compatible_range(self.package, &set.complement())
-                        .plural()
-                }
-            }
-        }
-    }
 }
 
 /// The kind of version ranges being displayed in [`PackageRange`]

crates/uv/tests/it/lock.rs

@@ -3232,7 +3232,7 @@ fn lock_requires_python() -> Result<()> {
 
     ----- stderr -----
       × No solution found when resolving dependencies for split (python_full_version >= '3.7' and python_full_version < '3.7.9'):
-      ╰─▶ Because the requested Python version (>=3.7) does not satisfy Python>=3.8 and the requested Python version (>=3.7) does not satisfy Python>=3.7.9,<3.8, we can conclude that Python>=3.7.9 is incompatible.
+      ╰─▶ Because the requested Python version (>=3.7) does not satisfy Python>=3.8 and the requested Python version (>=3.7) does not satisfy Python>=3.7.9,<3.8, we can conclude that Python>=3.7.9 cannot be used.
           And because pygls>=1.1.0,<=1.2.1 depends on Python>=3.7.9,<4 and only pygls<=1.3.0 is available, we can conclude that all of:
               pygls>=1.1.0,<1.3.0
               pygls>1.3.0

crates/uv/tests/it/pip_install_scenarios.rs

@@ -3725,15 +3725,15 @@ fn python_greater_than_current_excluded() {
       ╰─▶ Because the current Python version (3.9.[X]) does not satisfy Python>=3.10,<3.11 and the current Python version (3.9.[X]) does not satisfy Python>=3.12, we can conclude that all of:
               Python>=3.10,<3.11
               Python>=3.12
-           are incompatible.
+           cannot be used.
-          And because the current Python version (3.9.[X]) does not satisfy Python>=3.11,<3.12, we can conclude that Python>=3.10 is incompatible.
+          And because the current Python version (3.9.[X]) does not satisfy Python>=3.11,<3.12, we can conclude that Python>=3.10 cannot be used.
           And because package-a==2.0.0 depends on Python>=3.10 and only the following versions of package-a are available:
               package-a<=2.0.0
               package-a==3.0.0
               package-a==4.0.0
           we can conclude that package-a>=2.0.0,<3.0.0 cannot be used. (1)
 
-          Because the current Python version (3.9.[X]) does not satisfy Python>=3.11,<3.12 and the current Python version (3.9.[X]) does not satisfy Python>=3.12, we can conclude that Python>=3.11 is incompatible.
+          Because the current Python version (3.9.[X]) does not satisfy Python>=3.11,<3.12 and the current Python version (3.9.[X]) does not satisfy Python>=3.12, we can conclude that Python>=3.11 cannot be used.
           And because package-a==3.0.0 depends on Python>=3.11, we can conclude that package-a==3.0.0 cannot be used.
           And because we know from (1) that package-a>=2.0.0,<3.0.0 cannot be used, we can conclude that package-a>=2.0.0,<4.0.0 cannot be used. (2)