potential patch to broken symlink

src/nimblepkg/packageinstaller.nim

@@ -30,15 +30,25 @@ proc setupBinSymlink*(symlinkDest, symlinkFilename: string,
     symlinkDestRel = relativePath(symlinkDest, symlinkFilename.parentDir())
     currentPerms = getFilePermissions(symlinkDest)
   setFilePermissions(symlinkDest, currentPerms + {fpUserExec})
-  when defined(unix):
-    display("Creating", "symlink: $1 -> $2" %
-            [symlinkDest, symlinkFilename], priority = MediumPriority)
-    if fileExists(symlinkFilename):
+  when defined(unix):  
+    proc removeWithWarning() = 
       let msg = "Symlink already exists in $1. Replacing." % symlinkFilename
       display("Warning:", msg, Warning, HighPriority)
-      removeFile(symlinkFilename)
+      removeFile(symlinkFilename)  
 
-    createSymlink(symlinkDestRel, symlinkFilename)
+    display("Creating", "symlink: $1 -> $2" %
+            [symlinkDest, symlinkFilename], priority = MediumPriority)
+    if fileExists(symlinkFilename):
+      removeWithWarning()      
+    try:
+      createSymlink(symlinkDestRel, symlinkFilename)
+    except OSError as ex:
+      #fileExists may return false for broken symlink
+      if "File exists" in ex.msg:
+        removeWithWarning()
+        createSymlink(symlinkDestRel, symlinkFilename)
+      else:
+        raise ex
     result.add symlinkFilename.extractFilename
   elif defined(windows):
     # There is a bug on XP, described here: