use a released version of nix

db/Cargo.toml

@@ -24,7 +24,7 @@ libpasta = "0.1.0-rc2"
 log = "0.4"
 lru-cache = "0.1"
 mylog = { git = "https://github.com/scottlamb/mylog" }
-nix = { git = "https://github.com/nix-rust/nix" }
+nix = "0.16.1"
 odds = { version = "0.3.1", features = ["std-vec"] }
 openssl = "0.10"
 parking_lot = { version = "0.9", features = [] }

db/dir.rs

@@ -76,6 +76,7 @@ impl CompositeIdPath {
 }
 
 impl NixPath for CompositeIdPath {
+    fn is_empty(&self) -> bool { false }
     fn len(&self) -> usize { 16 }
 
     fn with_nix_path<T, F>(&self, f: F) -> Result<T, nix::Error>

db/upgrade/mod.rs

@@ -143,6 +143,7 @@ impl UuidPath {
 }
 
 impl NixPath for UuidPath {
+    fn is_empty(&self) -> bool { false }
     fn len(&self) -> usize { 36 }
 
     fn with_nix_path<T, F>(&self, f: F) -> Result<T, nix::Error>