log kernel specs that fail to load

IPython/html/services/kernelspecs/handlers.py

@@ -19,7 +19,11 b' class MainKernelSpecHandler(IPythonHandler):'
         ksm = self.kernel_spec_manager
         results = []
         for kernel_name in sorted(ksm.find_kernel_specs(), key=_pythonfirst):
+            try:
             d = ksm.get_kernel_spec(kernel_name).to_dict()
+            except Exception:
+                self.log.error("Failed to load kernel spec: '%s'", kernel_name, exc_info=True)
+                continue
             d['name'] = kernel_name
             results.append(d)
 

IPython/html/services/kernelspecs/tests/test_kernelspecs_api.py

@@ -5,6 +5,7 b' import errno'
 import io
 import json
 import os
+import shutil
 
 pjoin = os.path.join
 
@@ -66,6 +67,25 b' class APITest(NotebookTestBase):'
 
         self.ks_api = KernelSpecAPI(self.base_url())
 
+    def test_list_kernelspecs_bad(self):
+        """Can list kernelspecs when one is invalid"""
+        bad_kernel_dir = pjoin(self.ipython_dir.name, 'kernels', 'bad')
+        try:
+            os.makedirs(bad_kernel_dir)
+        except OSError as e:
+            if e.errno != errno.EEXIST:
+                raise
+        
+        with open(pjoin(bad_kernel_dir, 'kernel.json'), 'w') as f:
+            f.write("garbage")
+        
+        specs = self.ks_api.list().json()
+        assert isinstance(specs, list)
+        # 2: the sample kernelspec created in setUp, and the native Python kernel
+        self.assertGreaterEqual(len(specs), 2)
+        
+        shutil.rmtree(bad_kernel_dir)
+    
     def test_list_kernelspecs(self):
         specs = self.ks_api.list().json()
         assert isinstance(specs, list)