Feature: More verbose error messages for synapsectl configure

[calvinleng-science]

Summary

Added error messages for the following cases when using synapsectl -u foo configure and synapsectl -u foo start:

• Config JSON file not found
• Config JSON no read permissions
• file.read() generic exception message
  and more importantly:
• catching the exceptions informing about syntax errors in the config JSON file thrown by google.protobuf.json_format.Parse

Motivation

Previously, every single error in the configuration process would simply give this error message:

Uncaught error during function. Why: Could not parse ../app-name/config.json as either device configuration or manifest

This would be the case even if the file was not found, which was not informative if they typo'd the filename. The message would also be not informative if they did not have read permissions for the file. It now prints an informative error message for these cases.

The syntax error messages though is especially helpful, as it'll inform users on how to debug where syntax errors occur in their config. Now, it will print something along the lines of (Case: forgot ending quote):

[15:26:46]  Uncaught error during function. Why: Could not parse ../synapse-spike-detect/config/simulator.json as either format:                        __main__.py:96
             - DeviceConfiguration: Failed to load JSON: Expecting property name enclosed in double quotes: line 14 column 5 (char 257).                              
             - AppManifest: Failed to load JSON: Expecting property name enclosed in double quotes: line 14 column 5 (char 257).  

or something like (Case: forgot to put value in field)

[15:28:34]  Uncaught error during function. Why: Could not parse ../synapse-spike-detect/config/simulator.json as either format:                        __main__.py:96
             - DeviceConfiguration: Failed to load JSON: Expecting value: line 9 column 28 (char 180).                                                                
             - AppManifest: Failed to load JSON: Expecting value: line 9 column 28 (char 180).  

or even incompatibilities with Synapse API (Case: typo'd enum value w.r.t. Synapse API):

[15:29:00]  Uncaught error during function. Why: Could not parse ../synapse-spike-detect/config/simulator.json as either format:                        __main__.py:96
             - DeviceConfiguration: Failed to parse nodes field: Failed to parse type field: Invalid enum value kApplicationasdfasf for enum type                     
           synapse.NodeType at DeviceConfiguration.nodes[0].type..                                                                                                    
             - AppManifest: Message type "synapse.AppManifest" has no field named "nodes" at "AppManifest".                                                           
            Available Fields(except extensions): "['name', 'configSchema', 'deviceConfig']"  

[namthor9]

looks good!