Export ErrOSXFUSENotFound, callers want to check for it

mount.go

@@ -2,11 +2,21 @@ package fuse
 
 import (
 	"bufio"
+	"errors"
 	"io"
 	"log"
 	"sync"
 )
 
+var (
+	// ErrOSXFUSENotFound is returned from Mount when the OSXFUSE
+	// installation is not detected.
+	//
+	// Only happens on OS X. Make sure OSXFUSE is installed, or see
+	// OSXFUSELocations for customization.
+	ErrOSXFUSENotFound = errors.New("cannot locate OSXFUSE")
+)
+
 func neverIgnoreLine(line string) bool {
 	return false
 }

mount_darwin.go

@@ -14,9 +14,8 @@ import (
 )
 
 var (
-	errNoAvail         = errors.New("no available fuse devices")
-	errNotLoaded       = errors.New("osxfuse is not loaded")
-	errOSXFUSENotFound = errors.New("cannot locate OSXFUSE")
+	errNoAvail   = errors.New("no available fuse devices")
+	errNotLoaded = errors.New("osxfuse is not loaded")
 )
 
 func loadOSXFUSE(bin string) error {
@@ -202,5 +201,5 @@ func mount(dir string, conf *mountConfig, ready chan<- struct{}, errp *error) (*
 		}
 		return f, nil
 	}
-	return nil, errOSXFUSENotFound
+	return nil, ErrOSXFUSENotFound
 }