diff --git a/.coveragerc b/.coveragerc
index e05a8a7f..5e96c646 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -6,9 +6,11 @@ include = */pandas_datareader/*
 omit =
     */_version.py
     */yahoo/*
+    */edgar.py
     */google/options.py
     */google/quotes.py
     */tests/google/test_options.py
+    */tests/test_edgar.py
 
 [report]
 # Regexes for lines to exclude from consideration
diff --git a/pandas_datareader/base.py b/pandas_datareader/base.py
index 1a359fcf..200d6717 100644
--- a/pandas_datareader/base.py
+++ b/pandas_datareader/base.py
@@ -125,6 +125,7 @@ def _get_response(self, url, params=None, headers=None):
 
         # initial attempt + retry
         pause = self.pause
+        last_response_text = ''
         for i in range(self.retry_count + 1):
             response = self.session.get(url,
                                         params=params,
@@ -132,6 +133,7 @@ def _get_response(self, url, params=None, headers=None):
             if response.status_code == requests.codes.ok:
                 return response
 
+            last_response_text = response.text.encode(response.encoding)
             time.sleep(pause)
 
             # Increase time between subsequent requests, per subclass.
@@ -146,8 +148,11 @@ def _get_response(self, url, params=None, headers=None):
 
         if params is not None and len(params) > 0:
             url = url + "?" + urlencode(params)
+        msg = 'Unable to read URL: {0}'.format(url)
+        if last_response_text:
+            msg += '\nResponse Text:\n{0}'.format(last_response_text)
 
-        raise RemoteDataError('Unable to read URL: {0}'.format(url))
+        raise RemoteDataError(msg)
 
     def _get_crumb(self, *args):
         """ To be implemented by subclass """
diff --git a/pandas_datareader/compat/__init__.py b/pandas_datareader/compat/__init__.py
index 91724a7f..743050b6 100644
--- a/pandas_datareader/compat/__init__.py
+++ b/pandas_datareader/compat/__init__.py
@@ -1,10 +1,13 @@
 # flake8: noqa
+import sys
+from distutils.version import LooseVersion
+from io import BytesIO
+
 import pandas as pd
-import pandas.io.common as com
 import pandas.compat as compat
+import pandas.io.common as com
 
-from io import BytesIO
-from distutils.version import LooseVersion
+PY3 = sys.version_info >= (3, 0)
 
 PANDAS_VERSION = LooseVersion(pd.__version__)
 
diff --git a/pandas_datareader/tests/test_tiingo.py b/pandas_datareader/tests/test_tiingo.py
index 29f6057a..c656da19 100644
--- a/pandas_datareader/tests/test_tiingo.py
+++ b/pandas_datareader/tests/test_tiingo.py
@@ -3,10 +3,13 @@
 import pandas as pd
 import pytest
 
+from pandas_datareader.compat import PY3
 from pandas_datareader.tiingo import TiingoDailyReader, TiingoMetaDataReader, \
-    TiingoQuoteReader
+    TiingoQuoteReader, get_tiingo_symbols
 
 TEST_API_KEY = os.getenv('TIINGO_API_KEY')
+# Ensure blank TEST_API_KEY not used in pull request
+TEST_API_KEY = None if not TEST_API_KEY else TEST_API_KEY
 
 syms = ['GOOG', ['GOOG', 'XOM']]
 ids = list(map(str, syms))
@@ -42,3 +45,18 @@ def test_tiingo_metadata(symbols):
     if isinstance(symbols, str):
         symbols = [symbols]
     assert df.shape[1] == len(symbols)
+
+
+@pytest.mark.skipif(not PY3, reason='test.support missing on Python 2')
+def test_tiingo_no_api_key(symbols):
+    from test.support import EnvironmentVarGuard
+    env = EnvironmentVarGuard()
+    env.unset('TIINGO_API_KEY')
+    with env:
+        with pytest.raises(ValueError):
+            TiingoMetaDataReader(symbols=symbols)
+
+
+def test_tiingo_stock_symbols():
+    sym = get_tiingo_symbols()
+    assert isinstance(sym, pd.DataFrame)
diff --git a/pandas_datareader/tiingo.py b/pandas_datareader/tiingo.py
index eaed50e0..144ce064 100644
--- a/pandas_datareader/tiingo.py
+++ b/pandas_datareader/tiingo.py
@@ -58,8 +58,8 @@ def __init__(self, symbols, start=None, end=None, retry_count=3, pause=0.1,
             self.symbols = [self.symbols]
         self._symbol = ''
         if api_key is None:
-            api_key = os.environ.get('TIINGO_API_KEY', None)
-        if api_key is None:
+            api_key = os.getenv('TIINGO_API_KEY')
+        if not api_key or not isinstance(api_key, str):
             raise ValueError('The tiingo API key must be provided either '
                              'through the api_key variable or through the '
                              'environmental variable TIINGO_API_KEY.')