change multipart::Part::mime() to mime_str()

The mime crate is expecting a breaking change to 0.4, so to remove the
public dependency, this method is changed to `mime_str`, which will
parse a MIME string instead.

src/error.rs

@@ -113,6 +113,7 @@ impl Error {
         match self.kind {
             Kind::Http(ref e) => Some(e),
             Kind::Hyper(ref e) => Some(e),
+            Kind::Mime(ref e) => Some(e),
             Kind::Url(ref e) => Some(e),
             Kind::Tls(ref e) => Some(e),
             Kind::Io(ref e) => Some(e),
@@ -193,6 +194,7 @@ impl fmt::Display for Error {
         match self.kind {
             Kind::Http(ref e) => fmt::Display::fmt(e, f),
             Kind::Hyper(ref e) => fmt::Display::fmt(e, f),
+            Kind::Mime(ref e) => fmt::Display::fmt(e, f),
             Kind::Url(ref e) => fmt::Display::fmt(e, f),
             Kind::Tls(ref e) => fmt::Display::fmt(e, f),
             Kind::Io(ref e) => fmt::Display::fmt(e, f),
@@ -217,6 +219,7 @@ impl StdError for Error {
         match self.kind {
             Kind::Http(ref e) => e.description(),
             Kind::Hyper(ref e) => e.description(),
+            Kind::Mime(ref e) => e.description(),
             Kind::Url(ref e) => e.description(),
             Kind::Tls(ref e) => e.description(),
             Kind::Io(ref e) => e.description(),
@@ -233,6 +236,7 @@ impl StdError for Error {
         match self.kind {
             Kind::Http(ref e) => e.cause(),
             Kind::Hyper(ref e) => e.cause(),
+            Kind::Mime(ref e) => e.cause(),
             Kind::Url(ref e) => e.cause(),
             Kind::Tls(ref e) => e.cause(),
             Kind::Io(ref e) => e.cause(),
@@ -252,6 +256,7 @@ impl StdError for Error {
 pub enum Kind {
     Http(::http::Error),
     Hyper(::hyper::Error),
+    Mime(::mime::FromStrError),
     Url(::url::ParseError),
     Tls(::native_tls::Error),
     Io(io::Error),
@@ -274,9 +279,14 @@ impl From<::http::Error> for Kind {
 impl From<::hyper::Error> for Kind {
     #[inline]
     fn from(err: ::hyper::Error) -> Kind {
-        match err {
+        Kind::Hyper(err)
-            other => Kind::Hyper(other),
+    }
-        }
+}
+
+impl From<::mime::FromStrError> for Kind {
+    #[inline]
+    fn from(err: ::mime::FromStrError) -> Kind {
+        Kind::Mime(err)
     }
 }
 

src/multipart.rs

@@ -191,11 +191,19 @@ impl Part {
         }
     }
 
+    /// Tries to set the mime of this part.
+    pub fn mime_str(mut self, mime: &str) -> ::Result<Part> {
+        self.mime = Some(try_!(mime.parse()));
+        Ok(self)
+    }
+
+    /* Re-enable when mime 0.4 is available, with split MediaType/MediaRange.
     /// Sets the mime, builder style.
     pub fn mime(mut self, mime: Mime) -> Part {
         self.mime = Some(mime);
         self
     }
+    */
 
     /// Sets the filename, builder style.
     pub fn file_name<T: Into<Cow<'static, str>>>(mut self, filename: T) -> Part {