MAINT: Add onRejected funcs throughout plateViewer

These will alert the user if something goes wrong. This sort of
paradigm is already in use in this codebase, so adding these is pretty
simple -- essentially just giving a short summary of the issue,
then dumping the error message.

labcontrol/gui/static/js/plateViewer.js

@@ -508,22 +508,30 @@ PlateViewer.prototype.modifyWell = function(row, col, content) {
   var possiblyNewContent = content;
   // TODO: cache list of active samples so that we don't have to make this
   // particular request every time modifyWell() is called.
-  get_active_samples().then(function(sampleIDs) {
-    // If there is *exactly one* match with an active sample ID, use
-    // that instead. In any other case (0 matches or > 1 matches),
-    // manual resolution is required -- so we don't bother changing the
-    // cell content.
-    var matchingSamples = getSubstringMatches(content, sampleIDs);
-    if (matchingSamples.length === 1) {
-      possiblyNewContent = matchingSamples[0];
-      safeArrayDelete(that.wellClasses[row][col], "well-indeterminate");
-    } else if (matchingSamples.length > 1) {
-      addIfNotPresent(that.wellClasses[row][col], "well-indeterminate");
-    } else {
-      safeArrayDelete(that.wellClasses[row][col], "well-indeterminate");
+  get_active_samples().then(
+    function(sampleIDs) {
+      // If there is *exactly one* match with an active sample ID, use
+      // that instead. In any other case (0 matches or > 1 matches),
+      // manual resolution is required -- so we don't bother changing the
+      // cell content.
+      var matchingSamples = getSubstringMatches(content, sampleIDs);
+      if (matchingSamples.length === 1) {
+        possiblyNewContent = matchingSamples[0];
+        safeArrayDelete(that.wellClasses[row][col], "well-indeterminate");
+      } else if (matchingSamples.length > 1) {
+        addIfNotPresent(that.wellClasses[row][col], "well-indeterminate");
+      } else {
+        safeArrayDelete(that.wellClasses[row][col], "well-indeterminate");
+      }
+      that.patchWell(row, col, possiblyNewContent, studyID);
+    },
+    function(rejectionReason) {
+      bootstrapAlert(
+        "Attempting to get a list of sample IDs failed:" + rejectionReason,
+        "danger"
+      );
     }
-    that.patchWell(row, col, possiblyNewContent, studyID);
-  });
+  );
 };
 
 /**
@@ -797,20 +805,30 @@ function autocomplete_search_samples(request, response) {
     );
   });
 
-  $.when.apply($, requests).then(function() {
-    // The nature of arguments change based on the number of requests performed
-    // If only one request was performed, then arguments only contain the output
-    // of that request. On the other hand, if there was more than one request,
-    // then arguments is a list of results
-    var arg = requests.length === 1 ? [arguments] : arguments;
-    var samples = merge_sample_responses(arg);
-    // Format the samples in the way that autocomplete needs
-    var results = [];
-    $.each(samples, function(index, value) {
-      results.push({ label: value, value: value });
-    });
-    response(results);
-  });
+  $.when.apply($, requests).then(
+    function() {
+      // The nature of arguments change based on the number of requests performed
+      // If only one request was performed, then arguments only contain the output
+      // of that request. On the other hand, if there was more than one request,
+      // then arguments is a list of results
+      var arg = requests.length === 1 ? [arguments] : arguments;
+      var samples = merge_sample_responses(arg);
+      // Format the samples in the way that autocomplete needs
+      var results = [];
+      $.each(samples, function(index, value) {
+        results.push({ label: value, value: value });
+      });
+      response(results);
+    },
+    function(rejectionReason) {
+      bootstrapAlert(
+        "Attempting to get sample IDs while filling up the autocomplete " +
+          "dropdown menu failed: " +
+          rejectionReason,
+        "danger"
+      );
+    }
+  );
 }
 
 /**
@@ -888,10 +906,18 @@ function get_active_samples() {
     // sample IDs from all active studies
     // We're going to return a Promise, and this Promise's value will be the
     // array of all sample IDs from all active studies.
-    return $.when.apply($, requests).then(function() {
-      var arg = requests.length === 1 ? [arguments] : arguments;
-      return merge_sample_responses(arg);
-    });
+    return $.when.apply($, requests).then(
+      function() {
+        var arg = requests.length === 1 ? [arguments] : arguments;
+        return merge_sample_responses(arg);
+      },
+      function(rejectionReason) {
+        bootstrapAlert(
+          "Attempting to get a list of sample IDs failed:" + rejectionReason,
+          "danger"
+        );
+      }
+    );
   } else {
     return Promise.resolve([]);
   }