vsts: improve tracing

Adopt the dedicated trace method for handling exceptions.

Microsoft.Vsts.Authentication/BaseVstsAuthentication.cs

@@ -235,7 +235,8 @@ namespace Microsoft.Alm.Authentication
                     }
                     catch (HttpRequestException exception)
                     {
-                        context.Trace.WriteLine($"unable to get response from '{targetUri}' due to '{exception.Message}'.");
+                        context.Trace.WriteLine($"unable to get response from '{targetUri}', an error occurred before the server could respond.");
+                        context.Trace.WriteException(exception);
                     }
                 }
                 else
@@ -427,7 +428,8 @@ namespace Microsoft.Alm.Authentication
                 {
                     System.Diagnostics.Debug.WriteLine(exception);
 
-                    Trace.WriteLine($"failed to write credentials to the secure store: {exception.GetType().Name}.");
+                    Trace.WriteLine($"failed to write credentials to the secure store.");
+                    Trace.WriteException(exception);
                 }
             }
 
@@ -473,7 +475,8 @@ namespace Microsoft.Alm.Authentication
             {
                 System.Diagnostics.Debug.WriteLine(exception);
 
-                context.Trace.WriteLine($"failed to deserialize tenant cache: {exception.GetType().Name}.");
+                context.Trace.WriteLine($"failed to deserialize tenant cache.");
+                context.Trace.WriteException(exception);
 
                 return cache;
             }
@@ -579,7 +582,8 @@ namespace Microsoft.Alm.Authentication
             {
                 System.Diagnostics.Debug.WriteLine(exception);
 
-                context.Trace.WriteLine($"failed to serialize tenant cache: {exception.GetType().Name}.");
+                context.Trace.WriteLine($"failed to serialize tenant cache.");
+                context.Trace.WriteException(exception);
             }
         }
     }

Microsoft.Vsts.Authentication/TokenRegistry.cs

@@ -222,7 +222,7 @@ namespace Microsoft.Alm.Authentication
                 }
                 catch (Exception exception)
                 {
-                    context.Trace.WriteLine($"! {exception.Message}");
+                    context.Trace.WriteException(exception);
                 }
 
                 yield return result;

Microsoft.Vsts.Authentication/VstsAadAuthentication.cs

@@ -191,7 +191,7 @@ namespace Microsoft.Alm.Authentication
         /// <para/>
         /// Compact tokens are necessary for clients which have restrictions on the size of the basic authentication header which they can create (example: Git).
         /// </param>
-        [Obsolete("Please use Task<Credential> NoninteractiveLogon(TargetUri targetUri, PersonalAccessTokenOptions options) instead.", false)]
+        [Obsolete("Use Task<Credential> NoninteractiveLogon(TargetUri targetUri, PersonalAccessTokenOptions options) instead.", false)]
         public async Task<Credential> NoninteractiveLogon(TargetUri targetUri, bool requestCompactToken)
         {
             BaseSecureStore.ValidateTargetUri(targetUri);

Microsoft.Vsts.Authentication/VstsAdalTokenCache.cs

@@ -92,7 +92,8 @@ namespace Microsoft.Alm.Authentication
                     }
                     catch (Exception exception)
                     {
-                        _context.Trace.WriteLine($"error: {nameof(VstsAdalTokenCache)} \"{_cacheFilePath}\": {exception.Message}");
+                        _context.Trace.WriteLine($"error: {nameof(VstsAdalTokenCache)} \"{_cacheFilePath}\".");
+                        _context.Trace.WriteException(exception);
                     }
                 }
             }
@@ -114,7 +115,8 @@ namespace Microsoft.Alm.Authentication
                     }
                     catch (Exception exception)
                     {
-                        _context.Trace.WriteLine($"error: {nameof(VstsAdalTokenCache)} \"{_cacheFilePath}\": {exception.Message}");
+                        _context.Trace.WriteLine($"error: {nameof(VstsAdalTokenCache)} \"{_cacheFilePath}\".");
+                        _context.Trace.WriteException(exception);
                     }
                 }
             }