feat: Complete PyPI Query MCP Server Implementation (#3)

Merge pull request implementing complete PyPI query MCP server with comprehensive features and CI/CD pipeline.

pypi_query_mcp/core/exceptions.py

@@ -0,0 +1,56 @@
+"""Custom exceptions for PyPI Query MCP Server."""
+
+
+class PyPIError(Exception):
+    """Base exception for PyPI-related errors."""
+
+    def __init__(self, message: str, status_code: int = None):
+        super().__init__(message)
+        self.message = message
+        self.status_code = status_code
+
+
+class PackageNotFoundError(PyPIError):
+    """Raised when a package is not found on PyPI."""
+
+    def __init__(self, package_name: str):
+        message = f"Package '{package_name}' not found on PyPI"
+        super().__init__(message, status_code=404)
+        self.package_name = package_name
+
+
+class NetworkError(PyPIError):
+    """Raised when network-related errors occur."""
+
+    def __init__(self, message: str, original_error: Exception = None):
+        super().__init__(message)
+        self.original_error = original_error
+
+
+class RateLimitError(PyPIError):
+    """Raised when API rate limit is exceeded."""
+
+    def __init__(self, retry_after: int = None):
+        message = "PyPI API rate limit exceeded"
+        if retry_after:
+            message += f". Retry after {retry_after} seconds"
+        super().__init__(message, status_code=429)
+        self.retry_after = retry_after
+
+
+class InvalidPackageNameError(PyPIError):
+    """Raised when package name is invalid."""
+
+    def __init__(self, package_name: str):
+        message = f"Invalid package name: '{package_name}'"
+        super().__init__(message, status_code=400)
+        self.package_name = package_name
+
+
+class PyPIServerError(PyPIError):
+    """Raised when PyPI server returns a server error."""
+
+    def __init__(self, status_code: int, message: str = None):
+        if not message:
+            message = f"PyPI server error (HTTP {status_code})"
+        super().__init__(message, status_code=status_code)