Handle cases with symbolic bytecode (#1581)

* Fix issues with string code

* revert solc changes

myth

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 """mythril.py: Bug hunting on the Ethereum blockchain
-   http://www.github.com/b-mueller/mythril
+   http://www.github.com/ConsenSys/mythril
    """
 from sys import exit
 import mythril.interfaces.cli

mythril/laser/plugin/plugins/coverage/coverage_plugin.py

@@ -55,7 +55,10 @@ class InstructionCoveragePlugin(LaserPlugin):
                     cov_percentage = sum(code_cov[1]) / float(code_cov[0]) * 100
                 string_code = code
                 if type(code) == tuple:
-                    string_code = bytearray(code).hex()
+                    try:
+                        string_code = bytearray(code).hex()
+                    except TypeError:
+                        string_code = "<symbolic code>"
                 log.info(
                     "Achieved {:.2f}% coverage for code: {}".format(
                         cov_percentage, string_code