Adding suggestions when mbed detect fails

[bridadan]

This was added in response to #352.

Currently if a board that is unknown to mbed-ls is plugged in and then mbed detect is ran, the output isn't that helpful.

Inside of an mbed OS project:

$ mbed detect
WARNING:mbedls.lstools_base:Call to deprecated function get_details_txt. This method will be removed from the public API. Please use 'list_mbeds' instead

[mbed] Detected K64F, port COM18, mounted D:, interface version 0244:
[mbed] Supported toolchains for K64F
+--------+-----------+-----------+-----------+-----------+-----------+-----------+
| Target | mbed OS 2 | mbed OS 5 |    ARM    |  GCC_ARM  |    IAR    |   ARMC6   |
+--------+-----------+-----------+-----------+-----------+-----------+-----------+
| K64F   | Supported | Supported | Supported | Supported | Supported | Supported |
+--------+-----------+-----------+-----------+-----------+-----------+-----------+
Supported targets: 1
Supported toolchains: 4
Traceback (most recent call last):
  File "C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky\mbed-os\tools\detect_targets.py", line 82, in main
    if re.match(mcu_filter, mut['mcu']):
  File "c:\python27\lib\re.py", line 141, in match
    return _compile(pattern, flags).match(string)
TypeError: expected string or buffer
[ERROR] expected string or buffer
[mbed] ERROR: "c:\python27\python.exe" returned error code 1.
[mbed] ERROR: Command "c:\python27\python.exe -u C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky\mbed-os\tools\detect_targets.py" in "C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky"

Outside of an mbed OS project:

$ mbed detect
[mbed] WARNING: The mbed tools were not found in "C:\Users\bridan01\onedrive_arm\Documents\dev\parking-lot-viewer\google".
[mbed] WARNING: Limited information will be shown about connected mbed targets/boards
---
[mbed] Detected "K64F" connected to "D:" and using com port "COM18"
[mbed] Detected "None" connected to "E:" and using com port "COM7"

---

This PR changes the output to the following:

Inside of an mbed OS project:

$ mbed detect
[mbed] ERROR: Failed to correctly detect all targets (run with '-vv' for more information)

$ mbed detect -vv
[mbed] Working path "C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky" (program)
[mbed] Query "c:\python27\python.exe -u C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky\mbed-os\tools\detect_targets.py" in C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky
[mbed] Detected K64F, port COM18, mounted D:, interface version 0244:
[mbed] Supported toolchains for K64F
+--------+-----------+-----------+-----------+-----------+-----------+-----------+
| Target | mbed OS 2 | mbed OS 5 |    ARM    |  GCC_ARM  |    IAR    |   ARMC6   |
+--------+-----------+-----------+-----------+-----------+-----------+-----------+
| K64F   | Supported | Supported | Supported | Supported | Supported | Supported |
+--------+-----------+-----------+-----------+-----------+-----------+-----------+
Supported targets: 1
Supported toolchains: 4
Traceback (most recent call last):
  File "C:\Users\bridan01\onedrive_arm\Documents\dev\mbed-os-example-blinky\mbed-os\tools\detect_targets.py", line 82, in main
    if re.match(mcu_filter, mut['mcu']):
  File "c:\python27\lib\re.py", line 141, in match
    return _compile(pattern, flags).match(string)
TypeError: expected string or buffer
[ERROR] expected string or buffer
[mbed] ERROR: Failed to correctly detect all targets (run with '-vv' for more information)
---

Outside of an mbed OS project:

$ mbed detect
[mbed] WARNING: The mbed tools were not found in "C:\Users\bridan01\onedrive_arm\Documents\dev\parking-lot-viewer\google".
[mbed] WARNING: Limited information will be shown about connected mbed targets/boards
---
[mbed] Detected "K64F" connected to "D:" and using com port "COM18"
[mbed] Detected unknown target connected to "E:" and using com port "COM7"
[mbed] WARNING: If you're developing a new target, you can mock the device to continue your development. Use 'mbedls --mock ID:NAME' to do so (see 'mbedls --help' for more information)
---

NOTE: the traceback caused by the mbed os tools should probably be patched as well.

[screamerbg]

@bridadan please rebase

[bridadan]

Rebased!