add AIError to avoid crash

Sources/Prorsum/Net/Address.swift

@@ -149,7 +149,7 @@ public class Address {
 
         let ret = getaddrinfo(host, String(port), &hints, &addrInfoRef)
         guard ret == 0 else {
-            throw SystemError.lastOperationError!
+            throw AIError(errorNumber: ret) ?? SystemError.lastOperationError!
         }
 
         guard let addrList = addrInfoRef else {

Sources/Prorsum/POSIX/AIError.swift

@@ -0,0 +1,89 @@
+//
+//  AIError.swift
+//  AWSSDKSwift
+//
+//  Created by Yuki Takei on 2017/04/21.
+//
+//
+
+import Foundation
+
+#if os(Linux)
+    import Glibc
+#else
+    import Darwin.C
+#endif
+
+public enum AIError: Error {
+    // address
+    case addressfamily
+    case again
+    case badflags
+    case fail
+    case family
+    case memory
+    case nodata
+    case nonname
+    case service
+    case socktype
+    case system
+}
+
+extension AIError {
+    public init?(errorNumber: Int32) {
+        switch errorNumber {
+        case EAI_ADDRFAMILY: self = .addressfamily
+        case EAI_AGAIN: self = .again
+        case EAI_BADFLAGS: self = .badflags
+        case EAI_FAIL: self = .fail
+        case EAI_FAMILY: self = .family
+        case EAI_MEMORY: self = .memory
+        case EAI_NODATA: self = .nodata
+        case EAI_NONAME: self = .nonname
+        case EAI_SERVICE: self = .service
+        case EAI_SOCKTYPE: self = .socktype
+        case EAI_SYSTEM: self = .system
+        default:
+            return nil
+        }
+    }
+
+    public var errorNumber: Int32 {
+        switch self {
+        case .addressfamily:
+            return EAI_ADDRFAMILY
+        case .again:
+            return EAI_AGAIN
+        case .badflags:
+            return EAI_BADFLAGS
+        case .fail:
+            return EAI_FAIL
+        case .family:
+            return EAI_FAMILY
+        case .memory:
+            return EAI_MEMORY
+        case .nodata:
+            return EAI_NODATA
+        case .nonname:
+            return EAI_NONAME
+        case .service:
+            return EAI_SERVICE
+        case .socktype:
+            return EAI_SOCKTYPE
+        case .system:
+            return EAI_SYSTEM
+        }
+    }
+}
+
+extension AIError {
+    public static func description(for errorNumber: Int32) -> String {
+        return String(cString:  gai_strerror(errorNumber))
+    }
+}
+
+extension AIError : CustomStringConvertible {
+    public var description: String {
+        return AIError.description(for: self.errorNumber)
+    }
+}