From c66ca957d9a6c5adc2560042d802c29c966988c7 Mon Sep 17 00:00:00 2001
From: Matthias <xmatthias@outlook.com>
Date: Wed, 10 Jun 2020 19:57:47 +0200
Subject: [PATCH 1/2] Add test verifying this behaviour

---
 tests/pairlist/test_pairlist.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/tests/pairlist/test_pairlist.py b/tests/pairlist/test_pairlist.py
index 421f06911..c67f7ae1c 100644
--- a/tests/pairlist/test_pairlist.py
+++ b/tests/pairlist/test_pairlist.py
@@ -421,6 +421,23 @@ def test__whitelist_for_active_markets(mocker, whitelist_conf, markets, pairlist
     assert log_message in caplog.text
 
 
+@pytest.mark.parametrize("pairlist", AVAILABLE_PAIRLISTS)
+def test__whitelist_for_active_markets_empty(mocker, whitelist_conf, markets, pairlist, tickers):
+    whitelist_conf['pairlists'][0]['method'] = pairlist
+
+    mocker.patch('freqtrade.exchange.Exchange.exchange_has', return_value=True)
+
+    freqtrade = get_patched_freqtradebot(mocker, whitelist_conf)
+    mocker.patch.multiple('freqtrade.exchange.Exchange',
+                          markets=PropertyMock(return_value=None),
+                          get_tickers=tickers
+                          )
+    # Assign starting whitelist
+    pairlist_handler = freqtrade.pairlists._pairlist_handlers[0]
+    with pytest.raises(OperationalException, match=r'Markets not loaded.*'):
+        pairlist_handler._whitelist_for_active_markets(['ETH/BTC'])
+
+
 def test_volumepairlist_invalid_sortvalue(mocker, markets, whitelist_conf):
     whitelist_conf['pairlists'][0].update({"sort_key": "asdf"})
 

From 1e7826f3922748449554d01cfb81c7c366c5babb Mon Sep 17 00:00:00 2001
From: Matthias <xmatthias@outlook.com>
Date: Wed, 10 Jun 2020 19:57:59 +0200
Subject: [PATCH 2/2] Explicitly raise OperationalException if markets are not
 loaded correctly

---
 freqtrade/pairlist/IPairList.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/freqtrade/pairlist/IPairList.py b/freqtrade/pairlist/IPairList.py
index f48a7dcfd..fd25e0766 100644
--- a/freqtrade/pairlist/IPairList.py
+++ b/freqtrade/pairlist/IPairList.py
@@ -150,6 +150,9 @@ class IPairList(ABC):
         black_listed
         """
         markets = self._exchange.markets
+        if not markets:
+            raise OperationalException(
+                    'Markets not loaded. Make sure that exchange is initialized correctly.')
 
         sanitized_whitelist: List[str] = []
         for pair in pairlist: