Auto merge of #2576 - alexcrichton:silence-warnings-with-q, r=brson

Don't print warnings when -q is passed

Closes #2571

diff --cc src/cargo/core/shell.rs
index 1951cdeba10c128519cdc22a25f383342213ee24,95750ef34809b38e6ce9995337a8ce5c7abc99f7..b2241ada00a1c2120851e30fa66aa2479cdef57c
--- 1/src/cargo/core/shell.rs
--- 2/src/cargo/core/shell.rs
+++ b/src/cargo/core/shell.rs
@@@ -100,11 -100,29 +100,14 @@@ impl MultiShell 
      }
  
      pub fn warn<T: fmt::Display>(&mut self, message: T) -> CargoResult<()> {
-         self.err().say_status("warning:", message, YELLOW, false)
+         match self.verbosity {
+             Quiet => Ok(()),
+             _ => self.err().say_status("warning:", message, YELLOW, false),
+         }
      }
  
 -    pub fn set_verbosity(&mut self, verbose: bool, quiet: bool) -> CargoResult<()> {
 -        self.verbosity = match (verbose, quiet) {
 -            (true, true) => bail!("cannot set both --verbose and --quiet"),
 -            (true, false) => Verbose,
 -            (false, true) => Quiet,
 -            (false, false) => Normal
 -        };
 -        Ok(())
 -    }
 -
 -    /// shortcut for commands that don't have both --verbose and --quiet
 -    pub fn set_verbose(&mut self, verbose: bool) {
 -        if verbose {
 -            self.verbosity = Verbose;
 -        } else {
 -            self.verbosity = Normal;
 -        }
 +    pub fn set_verbosity(&mut self, verbosity: Verbosity) {
 +        self.verbosity = verbosity;
      }
  
      pub fn set_color_config(&mut self, color: Option<&str>) -> CargoResult<()> {