diff --git a/scripts/update_crate_tests.py b/scripts/update_crate_tests.py
index 53bfd83e0..477c65d9b 100755
--- a/scripts/update_crate_tests.py
+++ b/scripts/update_crate_tests.py
@@ -35,68 +35,68 @@ exclude_paths = [
         "//external/vm_tools"
     ]
 
+
+class UpdaterException(Exception):
+    pass
+
+
 class Env(object):
     def __init__(self, path):
         try:
             self.ANDROID_BUILD_TOP = os.environ['ANDROID_BUILD_TOP']
-        except:
-            sys.exit('ERROR: this script must be run from an Android tree.')
+        except KeyError:
+            raise UpdaterException('$ANDROID_BUILD_TOP is not defined; you '
+                                   'must first source build/envsetup.sh and '
+                                   'select a target.')
         if path == None:
             self.cwd = os.getcwd()
         else:
             self.cwd = path
         try:
             self.cwd_relative = self.cwd.split(self.ANDROID_BUILD_TOP)[1]
-            self.setup = True
-        except:
-            # Mark setup as failed if a path to a rust crate is not provided.
-            self.setup = False
+        except IndexError:
+            raise UpdaterException('The path ' + self.cwd + ' is not under ' +
+                            self.ANDROID_BUILD_TOP + '; You must be in the '
+                            'directory of a crate or pass its absolute path '
+                            'as first argument.')
+
 
 class Bazel(object):
     # set up the Bazel queryview
     def __init__(self, env):
+        if platform.system() != 'Linux':
+            raise UpdaterException('This script has only been tested on Linux.')
+        self.path = os.path.join(env.ANDROID_BUILD_TOP, "tools", "bazel")
         os.chdir(env.ANDROID_BUILD_TOP)
         print("Building Bazel Queryview. This can take a couple of minutes...")
         cmd = "./build/soong/soong_ui.bash --build-mode --all-modules --dir=. queryview"
         try:
-            out = subprocess.check_output(cmd, shell=True, stderr=subprocess.STDOUT)
-            self.setup = True
+            subprocess.check_output(cmd, shell=True, stderr=subprocess.STDOUT)
         except subprocess.CalledProcessError as e:
-            print("Error: Unable to update TEST_MAPPING due to the following build error:")
-            print(e.output)
-            # Mark setup as failed if the Bazel queryview fails to build.
-            self.setup = False
+            raise UpdaterException('Unable to update TEST_MAPPING: ' + e.output)
         os.chdir(env.cwd)
 
-    def path(self):
-        # Only tested on Linux.
-        if platform.system() != 'Linux':
-            sys.exit('ERROR: this script has only been tested on Linux.')
-        return "/usr/bin/bazel"
-
     # Return all modules for a given path.
     def query_modules(self, path):
-        with open(os.devnull, 'wb') as DEVNULL:
-            cmd = self.path() + " query --config=queryview /" + path + ":all"
-            out = subprocess.check_output(cmd, shell=True, stderr=DEVNULL, text=True).strip().split("\n")
-            modules = set()
-            for line in out:
-                # speed up by excluding unused modules.
-                if "windows_x86" in line:
-                    continue
-                modules.add(line)
-            return modules
+        cmd = self.path + " query --config=queryview /" + path + ":all"
+        out = subprocess.check_output(cmd, shell=True, stderr=subprocess.DEVNULL, text=True).strip().split("\n")
+        modules = set()
+        for line in out:
+            # speed up by excluding unused modules.
+            if "windows_x86" in line:
+                continue
+            modules.add(line)
+        return modules
 
     # Return all reverse dependencies for a single module.
     def query_rdeps(self, module):
-        with open(os.devnull, 'wb') as DEVNULL:
-            cmd = (self.path() + " query --config=queryview \'rdeps(//..., " +
-                    module + ")\' --output=label_kind")
-            out = (subprocess.check_output(cmd, shell=True, stderr=DEVNULL, text=True)
-                    .strip().split("\n"))
-            if '' in out:
-                out.remove('')
-            return out
+        cmd = (self.path + " query --config=queryview \'rdeps(//..., " +
+                module + ")\' --output=label_kind")
+        out = (subprocess.check_output(cmd, shell=True, stderr=subprocess.DEVNULL, text=True)
+                .strip().split("\n"))
+        if '' in out:
+            out.remove('')
+        return out
 
     def exclude_module(self, module):
         for path in exclude_paths:
@@ -130,12 +130,7 @@ class TestMapping(object):
         self.env = Env(path)
         self.bazel = Bazel(self.env)
 
-    def is_setup(self):
-        return self.env.setup and self.bazel.setup
-
     def create_test_mapping(self, path):
-        if not self.is_setup():
-            return
         tests = self.get_tests(path)
         if not bool(tests):
             return
@@ -173,10 +168,11 @@ def main():
         path = sys.argv[1]
     else:
         path = None
-    test_mapping = TestMapping(path)
+    try:
+        test_mapping = TestMapping(path)
+    except UpdaterException as err:
+        sys.exit("Error: " + str(err))
     test_mapping.create_test_mapping(None)
-    if not test_mapping.is_setup():
-        raise ValueError('Error getting crate tests.')
 
 if __name__ == '__main__':
   main()